diff --git a/backend/app/Events/InlineCommentAdded.php b/backend/app/Events/InlineCommentAdded.php
new file mode 100644
index 000000000..79df5bc23
--- /dev/null
+++ b/backend/app/Events/InlineCommentAdded.php
@@ -0,0 +1,42 @@
+<?php
+declare(strict_types=1);
+
+namespace App\Events;
+
+use App\Models\InlineComment;
+use Illuminate\Broadcasting\InteractsWithSockets;
+use Illuminate\Broadcasting\PrivateChannel;
+use Illuminate\Foundation\Events\Dispatchable;
+use Illuminate\Queue\SerializesModels;
+
+class InlineCommentAdded
+{
+    use Dispatchable;
+    use InteractsWithSockets;
+    use SerializesModels;
+
+    /**
+     * @var \App\Models\InlineComment $inline_comment
+     */
+    public $inline_comment;
+
+    /**
+     * @param \App\Models\InlineComment $inline_comment
+     */
+    public function __construct(InlineComment $inline_comment)
+    {
+        $this->inline_comment = $inline_comment;
+    }
+
+    /**
+     * Get the channels the event should broadcast on.
+     *
+     * @return array<int, \Illuminate\Broadcasting\Channel>
+     */
+    public function broadcastOn(): array
+    {
+        return [
+            new PrivateChannel('channel-name'),
+        ];
+    }
+}
diff --git a/backend/app/Events/InlineCommentReplyAdded.php b/backend/app/Events/InlineCommentReplyAdded.php
new file mode 100644
index 000000000..207c7acc4
--- /dev/null
+++ b/backend/app/Events/InlineCommentReplyAdded.php
@@ -0,0 +1,42 @@
+<?php
+declare(strict_types=1);
+
+namespace App\Events;
+
+use App\Models\InlineComment;
+use Illuminate\Broadcasting\InteractsWithSockets;
+use Illuminate\Broadcasting\PrivateChannel;
+use Illuminate\Foundation\Events\Dispatchable;
+use Illuminate\Queue\SerializesModels;
+
+class InlineCommentReplyAdded
+{
+    use Dispatchable;
+    use InteractsWithSockets;
+    use SerializesModels;
+
+    /**
+     * @var \App\Models\InlineComment $inline_comment
+     */
+    public $inline_comment;
+
+    /**
+     * @param \App\Models\InlineComment $inline_comment
+     */
+    public function __construct(InlineComment $inline_comment)
+    {
+        $this->inline_comment = $inline_comment;
+    }
+
+    /**
+     * Get the channels the event should broadcast on.
+     *
+     * @return array<int, \Illuminate\Broadcasting\Channel>
+     */
+    public function broadcastOn(): array
+    {
+        return [
+            new PrivateChannel('channel-name'),
+        ];
+    }
+}
diff --git a/backend/app/Events/OverallCommentAdded.php b/backend/app/Events/OverallCommentAdded.php
new file mode 100644
index 000000000..8817657c1
--- /dev/null
+++ b/backend/app/Events/OverallCommentAdded.php
@@ -0,0 +1,42 @@
+<?php
+declare(strict_types=1);
+
+namespace App\Events;
+
+use App\Models\OverallComment;
+use Illuminate\Broadcasting\InteractsWithSockets;
+use Illuminate\Broadcasting\PrivateChannel;
+use Illuminate\Foundation\Events\Dispatchable;
+use Illuminate\Queue\SerializesModels;
+
+class OverallCommentAdded
+{
+    use Dispatchable;
+    use InteractsWithSockets;
+    use SerializesModels;
+
+    /**
+     * @var \App\Models\OverallComment $overall_comment
+     */
+    public $overall_comment;
+
+    /**
+     * @param \App\Models\OverallComment $overall_comment
+     */
+    public function __construct(OverallComment $overall_comment)
+    {
+        $this->overall_comment = $overall_comment;
+    }
+
+    /**
+     * Get the channels the event should broadcast on.
+     *
+     * @return array<int, \Illuminate\Broadcasting\Channel>
+     */
+    public function broadcastOn(): array
+    {
+        return [
+            new PrivateChannel('channel-name'),
+        ];
+    }
+}
diff --git a/backend/app/Events/OverallCommentReplyAdded.php b/backend/app/Events/OverallCommentReplyAdded.php
new file mode 100644
index 000000000..fb95e4bf3
--- /dev/null
+++ b/backend/app/Events/OverallCommentReplyAdded.php
@@ -0,0 +1,42 @@
+<?php
+declare(strict_types=1);
+
+namespace App\Events;
+
+use App\Models\OverallComment;
+use Illuminate\Broadcasting\InteractsWithSockets;
+use Illuminate\Broadcasting\PrivateChannel;
+use Illuminate\Foundation\Events\Dispatchable;
+use Illuminate\Queue\SerializesModels;
+
+class OverallCommentReplyAdded
+{
+    use Dispatchable;
+    use InteractsWithSockets;
+    use SerializesModels;
+
+    /**
+     * @var \App\Models\OverallComment $overall_comment
+     */
+    public $overall_comment;
+
+    /**
+     * @param \App\Models\OverallComment $overall_comment
+     */
+    public function __construct(OverallComment $overall_comment)
+    {
+        $this->overall_comment = $overall_comment;
+    }
+
+    /**
+     * Get the channels the event should broadcast on.
+     *
+     * @return array<int, \Illuminate\Broadcasting\Channel>
+     */
+    public function broadcastOn(): array
+    {
+        return [
+            new PrivateChannel('channel-name'),
+        ];
+    }
+}
diff --git a/backend/app/Listeners/NotifyUsersAboutInlineComment.php b/backend/app/Listeners/NotifyUsersAboutInlineComment.php
new file mode 100644
index 000000000..f9908fbfc
--- /dev/null
+++ b/backend/app/Listeners/NotifyUsersAboutInlineComment.php
@@ -0,0 +1,46 @@
+<?php
+declare(strict_types=1);
+
+namespace App\Listeners;
+
+use App\Events\InlineCommentAdded as EventsInlineCommentAdded;
+use App\Notifications\InlineCommentAdded;
+use Illuminate\Bus\Queueable;
+use Illuminate\Contracts\Queue\ShouldQueue;
+use Illuminate\Support\Facades\Notification;
+
+class NotifyUsersAboutInlineComment extends Notification implements ShouldQueue
+{
+    use Queueable;
+
+    /**
+     * Handle the event.
+     *
+     * @param \App\Events\EventsInlineCommentAdded $event
+     * @return void
+     */
+    public function handle(EventsInlineCommentAdded $event): void
+    {
+        $submission = $event->inline_comment->submission;
+        $submitters = $submission->submitters()->get();
+        $review_coordinators = $submission->reviewCoordinators()->get();
+        $notification_data = [
+            'submission' => [
+                'id' => $submission->id,
+                'title' => $submission->title,
+            ],
+            'commentor' => [
+                'display_label' => $event->inline_comment->createdBy->displayLabel,
+            ],
+            'type' => 'submission.inline_comment.added',
+        ];
+        $recipients = $submitters
+            ->merge($review_coordinators)
+            ->unique()
+            ->filter(function ($user) use ($event) {
+                return $user->id !== $event->inline_comment->createdBy->id;
+            });
+
+        Notification::send($recipients, new InlineCommentAdded($notification_data));
+    }
+}
diff --git a/backend/app/Listeners/NotifyUsersAboutInlineCommentReply.php b/backend/app/Listeners/NotifyUsersAboutInlineCommentReply.php
new file mode 100644
index 000000000..e0c461e36
--- /dev/null
+++ b/backend/app/Listeners/NotifyUsersAboutInlineCommentReply.php
@@ -0,0 +1,50 @@
+<?php
+declare(strict_types=1);
+
+namespace App\Listeners;
+
+use App\Events\InlineCommentReplyAdded as EventsInlineCommentReplyAdded;
+use App\Notifications\InlineCommentReplyAdded;
+use Illuminate\Bus\Queueable;
+use Illuminate\Contracts\Queue\ShouldQueue;
+use Illuminate\Support\Facades\Notification;
+
+class NotifyUsersAboutInlineCommentReply extends Notification implements ShouldQueue
+{
+    use Queueable;
+
+    /**
+     * Handle the event.
+     *
+     * @param \App\Events\InlineCommentReplyAdded $event
+     * @return void
+     */
+    public function handle(EventsInlineCommentReplyAdded $event): void
+    {
+        $submission = $event->inline_comment->submission;
+        $submitters = $submission->submitters()->get();
+        $parent_commentor = $event->inline_comment->parent->createdBy()->get();
+        $commentors = $event->inline_comment->parent->commentors()->get();
+        $review_coordinators = $submission->reviewCoordinators()->get();
+        $notification_data = [
+            'submission' => [
+                'id' => $submission->id,
+                'title' => $submission->title,
+            ],
+            'commentor' => [
+                'display_label' => $event->inline_comment->createdBy->displayLabel,
+            ],
+            'type' => 'submission.inline_comment_reply.added',
+        ];
+        $recipients = $submitters
+            ->merge($commentors)
+            ->merge($parent_commentor)
+            ->merge($review_coordinators)
+            ->unique()
+            ->filter(function ($user) use ($event) {
+                return $user->id !== $event->inline_comment->createdBy->id;
+            });
+
+        Notification::send($recipients, new InlineCommentReplyAdded($notification_data));
+    }
+}
diff --git a/backend/app/Listeners/NotifyUsersAboutOverallComment.php b/backend/app/Listeners/NotifyUsersAboutOverallComment.php
new file mode 100644
index 000000000..560c59670
--- /dev/null
+++ b/backend/app/Listeners/NotifyUsersAboutOverallComment.php
@@ -0,0 +1,46 @@
+<?php
+declare(strict_types=1);
+
+namespace App\Listeners;
+
+use App\Events\OverallCommentAdded as EventsOverallCommentAdded;
+use App\Notifications\OverallCommentAdded;
+use Illuminate\Bus\Queueable;
+use Illuminate\Contracts\Queue\ShouldQueue;
+use Illuminate\Support\Facades\Notification;
+
+class NotifyUsersAboutOverallComment extends Notification implements ShouldQueue
+{
+    use Queueable;
+
+    /**
+     * Handle the event.
+     *
+     * @param \App\Events\EventsOverallCommentAdded $event
+     * @return void
+     */
+    public function handle(EventsOverallCommentAdded $event): void
+    {
+        $submission = $event->overall_comment->submission;
+        $submitters = $submission->submitters()->get();
+        $review_coordinators = $submission->reviewCoordinators()->get();
+        $notification_data = [
+            'submission' => [
+                'id' => $submission->id,
+                'title' => $submission->title,
+            ],
+            'commentor' => [
+                'display_label' => $event->overall_comment->createdBy->displayLabel,
+            ],
+            'type' => 'submission.overall_comment.added',
+        ];
+        $recipients = $submitters
+            ->merge($review_coordinators)
+            ->unique()
+            ->filter(function ($user) use ($event) {
+                return $user->id !== $event->overall_comment->createdBy->id;
+            });
+
+        Notification::send($recipients, new OverallCommentAdded($notification_data));
+    }
+}
diff --git a/backend/app/Listeners/NotifyUsersAboutOverallCommentReply.php b/backend/app/Listeners/NotifyUsersAboutOverallCommentReply.php
new file mode 100644
index 000000000..f07a64c9a
--- /dev/null
+++ b/backend/app/Listeners/NotifyUsersAboutOverallCommentReply.php
@@ -0,0 +1,50 @@
+<?php
+declare(strict_types=1);
+
+namespace App\Listeners;
+
+use App\Events\OverallCommentReplyAdded as EventsOverallCommentReplyAdded;
+use App\Notifications\OverallCommentReplyAdded;
+use Illuminate\Bus\Queueable;
+use Illuminate\Contracts\Queue\ShouldQueue;
+use Illuminate\Support\Facades\Notification;
+
+class NotifyUsersAboutOverallCommentReply extends Notification implements ShouldQueue
+{
+    use Queueable;
+
+    /**
+     * Handle the event.
+     *
+     * @param \App\Events\OverallCommentReplyAdded $event
+     * @return void
+     */
+    public function handle(EventsOverallCommentReplyAdded $event): void
+    {
+        $submission = $event->overall_comment->submission;
+        $submitters = $submission->submitters()->get();
+        $parent_commentor = $event->overall_comment->parent->createdBy()->get();
+        $commentors = $event->overall_comment->parent->commentors()->get();
+        $review_coordinators = $submission->reviewCoordinators()->get();
+        $notification_data = [
+            'submission' => [
+                'id' => $submission->id,
+                'title' => $submission->title,
+            ],
+            'commentor' => [
+                'display_label' => $event->overall_comment->createdBy->displayLabel,
+            ],
+            'type' => 'submission.overall_comment_reply.added',
+        ];
+        $recipients = $submitters
+            ->merge($commentors)
+            ->merge($parent_commentor)
+            ->merge($review_coordinators)
+            ->unique()
+            ->filter(function ($user) use ($event) {
+                return $user->id !== $event->overall_comment->createdBy->id;
+            });
+
+        Notification::send($recipients, new OverallCommentReplyAdded($notification_data));
+    }
+}
diff --git a/backend/app/Models/InlineComment.php b/backend/app/Models/InlineComment.php
index b6560c7a4..6b4ea393d 100644
--- a/backend/app/Models/InlineComment.php
+++ b/backend/app/Models/InlineComment.php
@@ -3,12 +3,15 @@
 
 namespace App\Models;
 
+use App\Events\InlineCommentAdded;
+use App\Events\InlineCommentReplyAdded;
 use App\Http\Traits\CreatedUpdatedBy;
 use App\Models\Traits\ReadStatus;
 use Illuminate\Database\Eloquent\Casts\Attribute;
 use Illuminate\Database\Eloquent\Factories\HasFactory;
 use Illuminate\Database\Eloquent\Relations\BelongsTo;
 use Illuminate\Database\Eloquent\Relations\HasMany;
+use Illuminate\Database\Eloquent\Relations\HasManyThrough;
 use Illuminate\Database\Eloquent\SoftDeletes;
 
 class InlineComment extends BaseModel
@@ -38,6 +41,21 @@ class InlineComment extends BaseModel
         'to',
     ];
 
+    /**
+     * @return void
+     */
+    protected static function boot()
+    {
+        parent::boot();
+        static::created(function ($inlineComment) {
+            if ($inlineComment->parent_id) {
+                InlineCommentReplyAdded::dispatch($inlineComment);
+            } else {
+                InlineCommentAdded::dispatch($inlineComment);
+            }
+        });
+    }
+
     /**
      * The submission that owns the inline comment
      *
@@ -63,6 +81,28 @@ public function replies(): HasMany
         }
     }
 
+    /**
+     * All commentors involved in the inline comment thread:
+     * - anyone who has replied to the parent inline comment or its replies
+     * - does not include the creator of the parent inline comment
+     *
+     * @return \Illuminate\Database\Eloquent\Relations\HasManyThrough
+     */
+    public function commentors(): HasManyThrough
+    {
+        $parentComment = $this->parent_id ? $this->parent : $this;
+
+        // Get all users who have replied to the parent inline comment
+        return $this->hasManyThrough(
+            User::class,
+            InlineComment::class,
+            'parent_id', // Foreign key on InlineComment table
+            'id', // Foreign key on User table
+            'id', // Local key on this table
+            'created_by' // Local key on InlineComment table
+        )->where('parent_id', $parentComment->id);
+    }
+
     /**
      * The creator of the inline comment
      *
@@ -83,6 +123,16 @@ public function updatedBy(): BelongsTo
         return $this->belongsTo(User::class, 'updated_by');
     }
 
+    /**
+     * The parent inline comment of this inline comment reply
+     *
+     * @return \Illuminate\Database\Eloquent\Relations\BelongsTo
+     */
+    public function parent(): BelongsTo
+    {
+        return $this->belongsTo(InlineComment::class, 'parent_id');
+    }
+
     /**
      * @return \Illuminate\Database\Eloquent\Casts\Attribute
      */
diff --git a/backend/app/Models/OverallComment.php b/backend/app/Models/OverallComment.php
index a696e08c0..c858ea1d1 100644
--- a/backend/app/Models/OverallComment.php
+++ b/backend/app/Models/OverallComment.php
@@ -3,12 +3,15 @@
 
 namespace App\Models;
 
+use App\Events\OverallCommentAdded;
+use App\Events\OverallCommentReplyAdded;
 use App\Http\Traits\CreatedUpdatedBy;
 use App\Models\Traits\ReadStatus;
 use Illuminate\Database\Eloquent\Casts\Attribute;
 use Illuminate\Database\Eloquent\Factories\HasFactory;
 use Illuminate\Database\Eloquent\Relations\BelongsTo;
 use Illuminate\Database\Eloquent\Relations\HasMany;
+use Illuminate\Database\Eloquent\Relations\HasManyThrough;
 use Illuminate\Database\Eloquent\SoftDeletes;
 
 class OverallComment extends BaseModel
@@ -30,6 +33,21 @@ class OverallComment extends BaseModel
         'parent_id',
     ];
 
+    /**
+     * @return void
+     */
+    protected static function boot()
+    {
+        parent::boot();
+        static::created(function ($overallComment) {
+            if ($overallComment->parent_id) {
+                OverallCommentReplyAdded::dispatch($overallComment);
+            } else {
+                OverallCommentAdded::dispatch($overallComment);
+            }
+        });
+    }
+
     /**
      * The submission that owns the overall comment
      *
@@ -55,6 +73,28 @@ public function replies(): HasMany
         }
     }
 
+    /**
+     * All commentors involved in the overall comment thread:
+     * - anyone who has replied to the parent overall comment or its replies
+     * - does not include the creator of the parent overall comment
+     *
+     * @return \Illuminate\Database\Eloquent\Relations\HasManyThrough
+     */
+    public function commentors(): HasManyThrough
+    {
+        $parentComment = $this->parent_id ? $this->parent : $this;
+
+        // Get all users who have replied to the parent overall comment
+        return $this->hasManyThrough(
+            User::class,
+            OverallComment::class,
+            'parent_id', // Foreign key on OverallComment table
+            'id', // Foreign key on User table
+            'id', // Local key on this table
+            'created_by' // Local key on OverallComment table
+        )->where('parent_id', $parentComment->id);
+    }
+
     /**
      * The creator of the overall comment
      *
@@ -75,6 +115,16 @@ public function updatedBy(): BelongsTo
         return $this->belongsTo(User::class, 'updated_by');
     }
 
+    /**
+     * The parent inline comment of this inline comment reply
+     *
+     * @return \Illuminate\Database\Eloquent\Relations\BelongsTo
+     */
+    public function parent(): BelongsTo
+    {
+        return $this->belongsTo(OverallComment::class, 'parent_id');
+    }
+
     /**
      * @return \Illuminate\Database\Eloquent\Casts\Attribute
      */
diff --git a/backend/app/Notifications/InlineCommentAdded.php b/backend/app/Notifications/InlineCommentAdded.php
new file mode 100644
index 000000000..58d153f9a
--- /dev/null
+++ b/backend/app/Notifications/InlineCommentAdded.php
@@ -0,0 +1,59 @@
+<?php
+declare(strict_types=1);
+
+namespace App\Notifications;
+
+use Illuminate\Bus\Queueable;
+use Illuminate\Contracts\Queue\ShouldQueue;
+use Illuminate\Notifications\Notification;
+
+class InlineCommentAdded extends Notification implements ShouldQueue
+{
+    use Queueable;
+
+    /**
+     * @var array
+     */
+    private $data;
+
+    /**
+     * Create a new notification instance.
+     *
+     * @param array $inline_comment
+     * @return void
+     */
+    public function __construct($inline_comment)
+    {
+        $this->data = $inline_comment;
+        $this->after_commit = true;
+    }
+
+    /**
+     * Get the notification's delivery channels.
+     *
+     * @return array<int, string>
+     */
+    public function via(): array
+    {
+        return ['database'];
+    }
+
+    /**
+     * Get the array representation of the notification.
+     *
+     * @return array<string, mixed>
+     */
+    public function toArray(): array
+    {
+        return [
+            'submission' => [
+                'id' => $this->data['submission']['id'],
+                'title' => $this->data['submission']['title'],
+            ],
+            'commentor' => [
+                'display_label' => $this->data['commentor']['display_label'],
+            ],
+            'type' => $this->data['type'],
+        ];
+    }
+}
diff --git a/backend/app/Notifications/InlineCommentReplyAdded.php b/backend/app/Notifications/InlineCommentReplyAdded.php
new file mode 100644
index 000000000..80acb818f
--- /dev/null
+++ b/backend/app/Notifications/InlineCommentReplyAdded.php
@@ -0,0 +1,58 @@
+<?php
+declare(strict_types=1);
+
+namespace App\Notifications;
+
+use Illuminate\Bus\Queueable;
+use Illuminate\Contracts\Queue\ShouldQueue;
+use Illuminate\Notifications\Notification;
+
+class InlineCommentReplyAdded extends Notification implements ShouldQueue
+{
+    use Queueable;
+
+    /**
+     * @var array
+     */
+    private $data;
+
+    /**
+     * Create a new notification instance.
+     *
+     * @param array $inline_comment
+     */
+    public function __construct($inline_comment)
+    {
+        $this->data = $inline_comment;
+        $this->after_commit = true;
+    }
+
+    /**
+     * Get the notification's delivery channels.
+     *
+     * @return array<int, string>
+     */
+    public function via(): array
+    {
+        return ['database'];
+    }
+
+    /**
+     * Get the array representation of the notification.
+     *
+     * @return array<string, mixed>
+     */
+    public function toArray(): array
+    {
+        return [
+            'submission' => [
+                'id' => $this->data['submission']['id'],
+                'title' => $this->data['submission']['title'],
+            ],
+            'commentor' => [
+                'display_label' => $this->data['commentor']['display_label'],
+            ],
+            'type' => $this->data['type'],
+        ];
+    }
+}
diff --git a/backend/app/Notifications/OverallCommentAdded.php b/backend/app/Notifications/OverallCommentAdded.php
new file mode 100644
index 000000000..e3668cc58
--- /dev/null
+++ b/backend/app/Notifications/OverallCommentAdded.php
@@ -0,0 +1,59 @@
+<?php
+declare(strict_types=1);
+
+namespace App\Notifications;
+
+use Illuminate\Bus\Queueable;
+use Illuminate\Contracts\Queue\ShouldQueue;
+use Illuminate\Notifications\Notification;
+
+class OverallCommentAdded extends Notification implements ShouldQueue
+{
+    use Queueable;
+
+    /**
+     * @var array
+     */
+    private $data;
+
+    /**
+     * Create a new notification instance.
+     *
+     * @param array $overall_comment
+     * @return void
+     */
+    public function __construct($overall_comment)
+    {
+        $this->data = $overall_comment;
+        $this->after_commit = true;
+    }
+
+    /**
+     * Get the notification's delivery channels.
+     *
+     * @return array<int, string>
+     */
+    public function via(): array
+    {
+        return ['database'];
+    }
+
+    /**
+     * Get the array representation of the notification.
+     *
+     * @return array<string, mixed>
+     */
+    public function toArray(): array
+    {
+        return [
+            'submission' => [
+                'id' => $this->data['submission']['id'],
+                'title' => $this->data['submission']['title'],
+            ],
+            'commentor' => [
+                'display_label' => $this->data['commentor']['display_label'],
+            ],
+            'type' => $this->data['type'],
+        ];
+    }
+}
diff --git a/backend/app/Notifications/OverallCommentReplyAdded.php b/backend/app/Notifications/OverallCommentReplyAdded.php
new file mode 100644
index 000000000..64bc9bf14
--- /dev/null
+++ b/backend/app/Notifications/OverallCommentReplyAdded.php
@@ -0,0 +1,58 @@
+<?php
+declare(strict_types=1);
+
+namespace App\Notifications;
+
+use Illuminate\Bus\Queueable;
+use Illuminate\Contracts\Queue\ShouldQueue;
+use Illuminate\Notifications\Notification;
+
+class OverallCommentReplyAdded extends Notification implements ShouldQueue
+{
+    use Queueable;
+
+    /**
+     * @var array
+     */
+    private $data;
+
+    /**
+     * Create a new notification instance.
+     *
+     * @param array $overall_comment
+     */
+    public function __construct($overall_comment)
+    {
+        $this->data = $overall_comment;
+        $this->after_commit = true;
+    }
+
+    /**
+     * Get the notification's delivery channels.
+     *
+     * @return array<int, string>
+     */
+    public function via(): array
+    {
+        return ['database'];
+    }
+
+    /**
+     * Get the array representation of the notification.
+     *
+     * @return array<string, mixed>
+     */
+    public function toArray(): array
+    {
+        return [
+            'submission' => [
+                'id' => $this->data['submission']['id'],
+                'title' => $this->data['submission']['title'],
+            ],
+            'commentor' => [
+                'display_label' => $this->data['commentor']['display_label'],
+            ],
+            'type' => $this->data['type'],
+        ];
+    }
+}
diff --git a/backend/app/Providers/EventServiceProvider.php b/backend/app/Providers/EventServiceProvider.php
index ec6235eae..476337a92 100644
--- a/backend/app/Providers/EventServiceProvider.php
+++ b/backend/app/Providers/EventServiceProvider.php
@@ -2,6 +2,10 @@
 
 namespace App\Providers;
 
+use App\Events\OverallCommentAdded;
+use App\Events\OverallCommentReplyAdded;
+use App\Events\InlineCommentAdded;
+use App\Events\InlineCommentReplyAdded;
 use App\Events\ReviewCoordinatorInvitationAccepted;
 use App\Events\ReviewCoordinatorInvited;
 use App\Events\ReviewerInvited;
@@ -11,6 +15,10 @@
 use App\Listeners\NotifyReviewerAboutInvitation;
 use App\Listeners\NotifyUsersAboutAcceptedReviewCoordinatorInvitation;
 use App\Listeners\NotifyUsersAboutAcceptedReviewerInvitation;
+use App\Listeners\NotifyUsersAboutInlineComment;
+use App\Listeners\NotifyUsersAboutInlineCommentReply;
+use App\Listeners\NotifyUsersAboutOverallComment;
+use App\Listeners\NotifyUsersAboutOverallCommentReply;
 use App\Listeners\NotifyUsersAboutUpdatedSubmissionStatus;
 use Illuminate\Auth\Events\Registered;
 use Illuminate\Auth\Listeners\SendEmailVerificationNotification;
@@ -47,6 +55,18 @@ class EventServiceProvider extends ServiceProvider
             'SocialiteProviders\Google\GoogleExtendSocialite@handle',
             'SocialiteProviders\Orcid\OrcidExtendSocialite@handle'
         ],
+        InlineCommentAdded::class => [
+            NotifyUsersAboutInlineComment::class,
+        ],
+        InlineCommentReplyAdded::class => [
+            NotifyUsersAboutInlineCommentReply::class,
+        ],
+        OverallCommentAdded::class => [
+            NotifyUsersAboutOverallComment::class,
+        ],
+        OverallCommentReplyAdded::class => [
+            NotifyUsersAboutOverallCommentReply::class,
+        ],
     ];
 
     /**
diff --git a/backend/graphql/notification.graphql b/backend/graphql/notification.graphql
index 38a2c7f31..7dcc8e0d9 100644
--- a/backend/graphql/notification.graphql
+++ b/backend/graphql/notification.graphql
@@ -27,6 +27,7 @@ type NotificationData {
     body: String
     action: String
     url: String
+    commentor: User
     invitee: User
     inviter: User
     submission: Submission
diff --git a/backend/phpunit.xml b/backend/phpunit.xml
index 588813d64..f7b05a3f3 100644
--- a/backend/phpunit.xml
+++ b/backend/phpunit.xml
@@ -6,9 +6,11 @@
     </testsuite>
     <testsuite name="Feature">
       <directory suffix="Test.php">./tests/Feature</directory>
+      <directory suffix="Test.php">./tests/Feature/Notifications</directory>
     </testsuite>
     <testsuite name="Api">
       <directory suffix="Test.php">./tests/Api</directory>
+      <directory suffix="Test.php">./tests/Api/Notifications</directory>
     </testsuite>
   </testsuites>
   <coverage/>
diff --git a/backend/tests/Api/NotificationTest.php b/backend/tests/Api/Notifications/SubmissionStatusUpdatesTest.php
similarity index 99%
rename from backend/tests/Api/NotificationTest.php
rename to backend/tests/Api/Notifications/SubmissionStatusUpdatesTest.php
index d3ced68bd..30f5ee4a0 100644
--- a/backend/tests/Api/NotificationTest.php
+++ b/backend/tests/Api/Notifications/SubmissionStatusUpdatesTest.php
@@ -1,7 +1,7 @@
 <?php
 declare(strict_types=1);
 
-namespace Tests\Api;
+namespace Tests\Api\Notifications;
 
 use App\Models\Publication;
 use App\Models\Submission;
@@ -11,7 +11,7 @@
 use Illuminate\Support\Facades\Notification;
 use Tests\ApiTestCase;
 
-class NotificationTest extends ApiTestCase
+class SubmissionStatusUpdatesTest extends ApiTestCase
 {
     use RefreshDatabase;
 
diff --git a/backend/tests/Api/SubmissionCommentTest.php b/backend/tests/Api/SubmissionCommentTest.php
index 08cac5eaf..4e9f5451c 100644
--- a/backend/tests/Api/SubmissionCommentTest.php
+++ b/backend/tests/Api/SubmissionCommentTest.php
@@ -5,93 +5,19 @@
 
 use App\Models\InlineComment;
 use App\Models\OverallComment;
-use App\Models\StyleCriteria;
 use App\Models\Submission;
-use App\Models\User;
 use Carbon\Carbon;
 use Illuminate\Foundation\Testing\RefreshDatabase;
 use Illuminate\Foundation\Testing\WithFaker;
 use Illuminate\Support\Str;
 use Tests\ApiTestCase;
+use Tests\TestFactory;
 
 class SubmissionCommentTest extends ApiTestCase
 {
     use WithFaker;
     use RefreshDatabase;
-
-    /**
-     * @param int $status (default: Submission::UNDER_REVIEW)
-     * @return Submission
-     */
-    private function createSubmission($status = Submission::UNDER_REVIEW)
-    {
-        $user = User::factory()->create();
-
-        return Submission::factory()
-            ->hasAttached($user, [], 'submitters')
-            ->create(['status' => $status]);
-    }
-
-    /**
-     * @param int $id
-     * @return StyleCriteria
-     */
-    private function createStyleCriteria($id)
-    {
-        $criteria = StyleCriteria::factory()
-            ->create([
-                'name' => 'PHPUnit Criteria',
-                'publication_id' => $id,
-                'description' => 'This is a test style criteria created by PHPUnit',
-                'icon' => 'php',
-            ]);
-
-        return $criteria;
-    }
-
-    /**
-     * @param int $count
-     * @param User|null $user (optional)
-     * @return Submission
-     */
-    private function createSubmissionWithInlineComment($count = 1, $user = null)
-    {
-        if ($user === null) {
-            $user = User::factory()->create();
-        }
-        $submission = $this->createSubmission();
-        $style_criteria = $this->createStyleCriteria($submission->publication->id);
-        InlineComment::factory()->count($count)->create([
-            'submission_id' => $submission->id,
-            'content' => 'This is some content for an inline comment created by PHPUnit.',
-            'created_by' => $user->id,
-            'updated_by' => $user->id,
-            'style_criteria' => [$style_criteria],
-        ]);
-
-        return $submission;
-    }
-
-    /**
-     * @param int $count
-     * @param User|null $user (optional)
-     * @return Submission
-     */
-    private function createSubmissionWithOverallComment($count = 1, $user = null)
-    {
-        if ($user === null) {
-            $user = User::factory()->create();
-        }
-        $submission = $this->createSubmission();
-        OverallComment::factory()->count($count)->create([
-            'submission_id' => $submission->id,
-            'content' => 'This is some content for an overall comment created by PHPUnit.',
-            'created_by' => $user->id,
-            'updated_by' => $user->id,
-        ]);
-
-        return $submission;
-    }
+    use TestFactory;
 
     public function testRetrieveInlineComments()
     {
diff --git a/backend/tests/Feature/Notifications/InlineCommentsTest.php b/backend/tests/Feature/Notifications/InlineCommentsTest.php
new file mode 100644
index 000000000..3dcfc9382
--- /dev/null
+++ b/backend/tests/Feature/Notifications/InlineCommentsTest.php
@@ -0,0 +1,159 @@
+<?php
+declare(strict_types=1);
+
+namespace Tests\Feature\Notifications;
+
+use App\Models\InlineComment;
+use App\Models\User;
+use Tests\TestCase;
+use Tests\TestFactory;
+
+class InlineCommentsTest extends TestCase
+{
+    use TestFactory;
+
+    private function createSubmissionWithInlineCommentThread()
+    {
+        $submission = $this->createSubmissionWithAllRoles();
+
+        // Create comment participants
+        $commentor = User::factory()->create();
+        $commentor_reply = User::factory()->create();
+        $commentor_reply_to_reply = User::factory()->create();
+        $commentor_elsewhere = User::factory()->create();
+
+        // Assign comment participants as submission reviewers
+        $submission->reviewers()->attach([
+            $commentor->id,
+            $commentor_reply->id,
+            $commentor_reply_to_reply->id,
+            $commentor_elsewhere->id,
+        ]);
+
+        // Make comments
+        InlineComment::factory()->create([
+            'submission_id' => $submission->id,
+            'content' => 'This is some content for an inline comment created by PHPUnit.',
+            'created_by' => $commentor_elsewhere->id,
+            'updated_by' => $commentor_elsewhere->id,
+            'style_criteria' => [],
+            'parent_id' => null,
+            'reply_to_id' => null,
+        ]);
+        $comment_parent = InlineComment::factory()->create([
+            'submission_id' => $submission->id,
+            'content' => 'This is some content for an inline comment created by PHPUnit.',
+            'created_by' => $commentor->id,
+            'updated_by' => $commentor->id,
+            'style_criteria' => [],
+            'parent_id' => null,
+            'reply_to_id' => null,
+        ]);
+        $comment_reply = InlineComment::factory()->create([
+            'submission_id' => $submission->id,
+            'content' => 'This is some content for an inline comment reply created by PHPUnit.',
+            'created_by' => $commentor_reply->id,
+            'updated_by' => $commentor_reply->id,
+            'style_criteria' => [],
+            'parent_id' => $comment_parent->id,
+            'reply_to_id' => $comment_parent->id,
+        ]);
+        InlineComment::factory()->create([
+            'submission_id' => $submission->id,
+            'content' => 'This is some content for an inline comment reply to a reply created by PHPUnit.',
+            'created_by' => $commentor_reply_to_reply->id,
+            'updated_by' => $commentor_reply_to_reply->id,
+            'style_criteria' => [],
+            'parent_id' => $comment_parent->id,
+            'reply_to_id' => $comment_reply->id,
+        ]);
+
+        return $submission;
+    }
+
+    /**
+     * @return void
+     */
+    public function testUsersReceiveNotificationsForNewInlineComments()
+    {
+        $submission = $this->createSubmissionWithInlineCommentThread();
+        $comments = $submission->inlineCommentsWithReplies();
+        $this->assertEquals(4, $comments->count());
+
+        // Submitter
+        // Gets all 4 notifications
+        $submitter = $submission->submitters()->first();
+        $this->assertEquals(2, $this->getInlineCommentNotificationCount($submitter));
+        $this->assertEquals(2, $this->getInlineCommentReplyNotificationCount($submitter));
+
+        // Uninvolved First Reviewer
+        // Gets 0 notifications
+        $reviewer1 = $submission->reviewers()->first();
+        $this->assertEquals(0, $this->getInlineCommentNotificationCount($reviewer1));
+        $this->assertEquals(0, $this->getInlineCommentReplyNotificationCount($reviewer1));
+
+        // Inline Commentor
+        // Gets 2 notifications for all replies
+        $reviewer2 = $submission->reviewers()->get()->slice(1, 1)->first();
+        $this->assertEquals(0, $this->getInlineCommentNotificationCount($reviewer2));
+        $this->assertEquals(2, $this->getInlineCommentReplyNotificationCount($reviewer2));
+
+        // Inline Comment Replier
+        // Gets 1 notification for reply to reply
+        $reviewer3 = $submission->reviewers()->get()->slice(2, 1)->first();
+        $this->assertEquals(0, $this->getInlineCommentNotificationCount($reviewer3));
+        $this->assertEquals(1, $this->getInlineCommentReplyNotificationCount($reviewer3));
+
+        // Inline Comment Reply Replier
+        // Gets 0 notifications
+        $reviewer4 = $submission->reviewers()->get()->slice(3, 1)->first();
+        $this->assertEquals(0, $this->getInlineCommentNotificationCount($reviewer4));
+        $this->assertEquals(0, $this->getInlineCommentReplyNotificationCount($reviewer4));
+
+        // Separate Inline Commentor
+        // Gets 0 notifications
+        $reviewer5 = $submission->reviewers()->first();
+        $this->assertEquals(0, $this->getInlineCommentNotificationCount($reviewer5));
+        $this->assertEquals(0, $this->getInlineCommentReplyNotificationCount($reviewer5));
+
+        // Coordinator
+        // Gets all 4 notifications
+        $coordinator = $submission->reviewCoordinators()->first();
+        $this->assertEquals(2, $this->getInlineCommentNotificationCount($coordinator));
+        $this->assertEquals(2, $this->getInlineCommentReplyNotificationCount($coordinator));
+
+        // Editor
+        // Gets 0 notifications
+        $editor = $submission->publication->editors()->first();
+        $this->assertEquals(0, $this->getInlineCommentNotificationCount($editor));
+        $this->assertEquals(0, $this->getInlineCommentReplyNotificationCount($editor));
+
+        // Publication Admins
+        // Gets 0 notifications
+        $admin = $submission->publication->publicationAdmins()->first();
+        $this->assertEquals(0, $this->getInlineCommentNotificationCount($admin));
+        $this->assertEquals(0, $this->getInlineCommentReplyNotificationCount($admin));
+    }
+
+    /**
+     * @param User $user
+     * @return int
+     */
+    private function getInlineCommentNotificationCount($user)
+    {
+        $type = 'App\Notifications\InlineCommentAdded';
+
+        return $user->notifications()->where('type', $type)->get()->count();
+    }
+
+    /**
+     * @param User $user
+     * @return int
+     */
+    private function getInlineCommentReplyNotificationCount($user)
+    {
+        $type = 'App\Notifications\InlineCommentReplyAdded';
+
+        return $user->notifications()->where('type', $type)->get()->count();
+    }
+}
diff --git a/backend/tests/Feature/Notifications/InvitationsTest.php b/backend/tests/Feature/Notifications/InvitationsTest.php
new file mode 100644
index 000000000..6ceb51a40
--- /dev/null
+++ b/backend/tests/Feature/Notifications/InvitationsTest.php
@@ -0,0 +1,78 @@
+<?php
+declare(strict_types=1);
+
+namespace Tests\Feature\Notifications;
+
+use App\Models\Role;
+use App\Models\Submission;
+use App\Models\SubmissionInvitation;
+use App\Models\User;
+use Tests\TestCase;
+use Tests\TestFactory;
+
+class InvitationsTest extends TestCase
+{
+    use TestFactory;
+
+    /**
+     * @return void
+     */
+    public function testSubmissionUsersReceiveNotificationsUponAcceptedReviewerInvitations()
+    {
+        $this->beAppAdmin();
+        $submitter = User::factory()->create();
+        $reviewer = User::factory()->create();
+        $review_coordinator = User::factory()->create();
+        $submission = Submission::factory()
+            ->hasAttached($submitter, [], 'submitters')
+            ->hasAttached($reviewer, [], 'reviewers')
+            ->hasAttached($review_coordinator, [], 'reviewCoordinators')
+            ->create();
+        $invite = SubmissionInvitation::create([
+            'submission_id' => $submission->id,
+            'role_id' => Role::REVIEWER_ROLE_ID,
+            'email' => 'bob1@msu.edu',
+        ]);
+        $invite->inviteReviewer();
+        $details = [
+            'name' => '',
+            'username' => 'bob1',
+            'password' => 'rLT2ovkZkMby5UpwiQkFBeS9',
+        ];
+        $invite->acceptInvite($details);
+        $this->assertEquals(1, $submitter->notifications->count());
+        $this->assertEquals(1, $reviewer->notifications->count());
+        $this->assertEquals(1, $review_coordinator->notifications->count());
+    }
+
+    /**
+     * @return void
+     */
+    public function testSubmissionUsersReceiveNotificationsUponAcceptedReviewCoordinatorInvitations()
+    {
+        $this->beAppAdmin();
+        $submitter = User::factory()->create();
+        $reviewer = User::factory()->create();
+        $review_coordinator = User::factory()->create();
+        $submission = Submission::factory()
+            ->hasAttached($submitter, [], 'submitters')
+            ->hasAttached($reviewer, [], 'reviewers')
+            ->hasAttached($review_coordinator, [], 'reviewCoordinators')
+            ->create();
+        $invite = SubmissionInvitation::create([
+            'submission_id' => $submission->id,
+            'role_id' => Role::REVIEW_COORDINATOR_ROLE_ID,
+            'email' => 'bob2@msu.edu',
+        ]);
+        $invite->inviteReviewCoordinator();
+        $details = [
+            'name' => '',
+            'username' => 'bob2',
+            'password' => 'aYUB1IYUadd38fl9mxAVv2',
+        ];
+        $invite->acceptInvite($details);
+        $this->assertEquals(1, $submitter->notifications->count());
+        $this->assertEquals(1, $reviewer->notifications->count());
+        $this->assertEquals(1, $review_coordinator->notifications->count());
+    }
+}
diff --git a/backend/tests/Feature/Notifications/OverallCommentsTest.php b/backend/tests/Feature/Notifications/OverallCommentsTest.php
new file mode 100644
index 000000000..6e62e4f1f
--- /dev/null
+++ b/backend/tests/Feature/Notifications/OverallCommentsTest.php
@@ -0,0 +1,155 @@
+<?php
+declare(strict_types=1);
+
+namespace Tests\Feature\Notifications;
+
+use App\Models\OverallComment;
+use App\Models\User;
+use Tests\TestCase;
+use Tests\TestFactory;
+
+class OverallCommentsTest extends TestCase
+{
+    use TestFactory;
+
+    private function createSubmissionWithOverallCommentThread()
+    {
+        $submission = $this->createSubmissionWithAllRoles();
+
+        // Create comment participants
+        $commentor = User::factory()->create();
+        $commentor_reply = User::factory()->create();
+        $commentor_reply_to_reply = User::factory()->create();
+        $commentor_elsewhere = User::factory()->create();
+
+        // Assign comment participants as submission reviewers
+        $submission->reviewers()->attach([
+            $commentor->id,
+            $commentor_reply->id,
+            $commentor_reply_to_reply->id,
+            $commentor_elsewhere->id,
+        ]);
+
+        // Make comments
+        OverallComment::factory()->create([
+            'submission_id' => $submission->id,
+            'content' => 'This is some content for an overall comment created by PHPUnit.',
+            'created_by' => $commentor_elsewhere->id,
+            'updated_by' => $commentor_elsewhere->id,
+            'parent_id' => null,
+            'reply_to_id' => null,
+        ]);
+        $comment_parent = OverallComment::factory()->create([
+            'submission_id' => $submission->id,
+            'content' => 'This is some content for an overall comment created by PHPUnit.',
+            'created_by' => $commentor->id,
+            'updated_by' => $commentor->id,
+            'parent_id' => null,
+            'reply_to_id' => null,
+        ]);
+        $comment_reply = OverallComment::factory()->create([
+            'submission_id' => $submission->id,
+            'content' => 'This is some content for an overall comment reply created by PHPUnit.',
+            'created_by' => $commentor_reply->id,
+            'updated_by' => $commentor_reply->id,
+            'parent_id' => $comment_parent->id,
+            'reply_to_id' => $comment_parent->id,
+        ]);
+        OverallComment::factory()->create([
+            'submission_id' => $submission->id,
+            'content' => 'This is some content for an overall comment reply to a reply created by PHPUnit.',
+            'created_by' => $commentor_reply_to_reply->id,
+            'updated_by' => $commentor_reply_to_reply->id,
+            'parent_id' => $comment_parent->id,
+            'reply_to_id' => $comment_reply->id,
+        ]);
+
+        return $submission;
+    }
+
+    /**
+     * @return void
+     */
+    public function testUsersReceiveNotificationsForNewOverallComments()
+    {
+        $submission = $this->createSubmissionWithOverallCommentThread();
+        $comments = $submission->overallCommentsWithReplies();
+        $this->assertEquals(4, $comments->count());
+
+        // Submitter
+        // Gets all 4 notifications
+        $submitter = $submission->submitters()->first();
+        $this->assertEquals(2, $this->getOverallCommentNotificationCount($submitter));
+        $this->assertEquals(2, $this->getOverallCommentReplyNotificationCount($submitter));
+
+        // Uninvolved First Reviewer
+        // Gets 0 notifications
+        $reviewer1 = $submission->reviewers()->first();
+        $this->assertEquals(0, $this->getOverallCommentNotificationCount($reviewer1));
+        $this->assertEquals(0, $this->getOverallCommentReplyNotificationCount($reviewer1));
+
+        // Overall Commentor
+        // Gets 2 notifications for all replies
+        $reviewer2 = $submission->reviewers()->get()->slice(1, 1)->first();
+        $this->assertEquals(0, $this->getOverallCommentNotificationCount($reviewer2));
+        $this->assertEquals(2, $this->getOverallCommentReplyNotificationCount($reviewer2));
+
+        // Overall Comment Replier
+        // Gets 1 notification for reply to reply
+        $reviewer3 = $submission->reviewers()->get()->slice(2, 1)->first();
+        $this->assertEquals(0, $this->getOverallCommentNotificationCount($reviewer3));
+        $this->assertEquals(1, $this->getOverallCommentReplyNotificationCount($reviewer3));
+
+        // Overall Comment Reply Replier
+        // Gets 0 notifications
+        $reviewer4 = $submission->reviewers()->get()->slice(3, 1)->first();
+        $this->assertEquals(0, $this->getOverallCommentNotificationCount($reviewer4));
+        $this->assertEquals(0, $this->getOverallCommentReplyNotificationCount($reviewer4));
+
+        // Separate overall Commentor
+        // Gets 0 notifications
+        $reviewer5 = $submission->reviewers()->first();
+        $this->assertEquals(0, $this->getOverallCommentNotificationCount($reviewer5));
+        $this->assertEquals(0, $this->getOverallCommentReplyNotificationCount($reviewer5));
+
+        // Coordinator
+        // Gets all 4 notifications
+        $coordinator = $submission->reviewCoordinators()->first();
+        $this->assertEquals(2, $this->getOverallCommentNotificationCount($coordinator));
+        $this->assertEquals(2, $this->getOverallCommentReplyNotificationCount($coordinator));
+
+        // Editor
+        // Gets 0 notifications
+        $editor = $submission->publication->editors()->first();
+        $this->assertEquals(0, $this->getOverallCommentNotificationCount($editor));
+        $this->assertEquals(0, $this->getOverallCommentReplyNotificationCount($editor));
+
+        // Publication Admins
+        // Gets 0 notifications
+        $admin = $submission->publication->publicationAdmins()->first();
+        $this->assertEquals(0, $this->getOverallCommentNotificationCount($admin));
+        $this->assertEquals(0, $this->getOverallCommentReplyNotificationCount($admin));
+    }
+
+    /**
+     * @param User $user
+     * @return int
+     */
+    private function getOverallCommentNotificationCount($user)
+    {
+        $type = 'App\Notifications\OverallCommentAdded';
+
+        return $user->notifications()->where('type', $type)->get()->count();
+    }
+
+    /**
+     * @param User $user
+     * @return int
+     */
+    private function getOverallCommentReplyNotificationCount($user)
+    {
+        $type = 'App\Notifications\OverallCommentReplyAdded';
+
+        return $user->notifications()->where('type', $type)->get()->count();
+    }
+}
diff --git a/backend/tests/Feature/NotificationTest.php b/backend/tests/Feature/Notifications/SubmissionStatusUpdatesTest.php
similarity index 73%
rename from backend/tests/Feature/NotificationTest.php
rename to backend/tests/Feature/Notifications/SubmissionStatusUpdatesTest.php
index 6467e93da..7778fb5b2 100644
--- a/backend/tests/Feature/NotificationTest.php
+++ b/backend/tests/Feature/Notifications/SubmissionStatusUpdatesTest.php
@@ -1,20 +1,20 @@
 <?php
 declare(strict_types=1);
 
-namespace Tests\Feature;
+namespace Tests\Feature\Notifications;
 
-use App\Models\Role;
 use App\Models\Submission;
-use App\Models\SubmissionInvitation;
 use App\Models\User;
 use App\Notifications\SubmissionStatusUpdated;
 use Illuminate\Foundation\Testing\RefreshDatabase;
 use Illuminate\Support\Facades\Notification;
 use Tests\TestCase;
+use Tests\TestFactory;
 
-class NotificationTest extends TestCase
+class SubmissionStatusUpdatesTest extends TestCase
 {
     use RefreshDatabase;
+    use TestFactory;
 
     /**
      * @param User $user
@@ -174,66 +174,4 @@ public function testMarkingMultipleSubmissionStatusUpdatedNotificationsAsReadFor
             $this->assertEquals(0, $user->unreadNotifications->count());
         });
     }
-
-    /**
-     * @return void
-     */
-    public function testSubmissionUsersReceiveNotificationsUponAcceptedReviewerInvitations()
-    {
-        $this->beAppAdmin();
-        $submitter = User::factory()->create();
-        $reviewer = User::factory()->create();
-        $review_coordinator = User::factory()->create();
-        $submission = Submission::factory()
-            ->hasAttached($submitter, [], 'submitters')
-            ->hasAttached($reviewer, [], 'reviewers')
-            ->hasAttached($review_coordinator, [], 'reviewCoordinators')
-            ->create();
-        $invite = SubmissionInvitation::create([
-            'submission_id' => $submission->id,
-            'role_id' => Role::REVIEWER_ROLE_ID,
-            'email' => 'bob@msu.edu',
-        ]);
-        $invite->inviteReviewer();
-        $details = [
-            'name' => '',
-            'username' => 'bob',
-            'password' => 'rLT2ovkZkMby5UpwiQkFBeS9',
-        ];
-        $invite->acceptInvite($details);
-        $this->assertEquals(1, $submitter->notifications->count());
-        $this->assertEquals(1, $reviewer->notifications->count());
-        $this->assertEquals(1, $review_coordinator->notifications->count());
-    }
-
-    /**
-     * @return void
-     */
-    public function testSubmissionUsersReceiveNotificationsUponAcceptedReviewCoordinatorInvitations()
-    {
-        $this->beAppAdmin();
-        $submitter = User::factory()->create();
-        $reviewer = User::factory()->create();
-        $review_coordinator = User::factory()->create();
-        $submission = Submission::factory()
-            ->hasAttached($submitter, [], 'submitters')
-            ->hasAttached($reviewer, [], 'reviewers')
-            ->hasAttached($review_coordinator, [], 'reviewCoordinators')
-            ->create();
-        $invite = SubmissionInvitation::create([
-            'submission_id' => $submission->id,
-            'role_id' => Role::REVIEW_COORDINATOR_ROLE_ID,
-            'email' => 'bob@msu.edu',
-        ]);
-        $invite->inviteReviewCoordinator();
-        $details = [
-            'name' => '',
-            'username' => 'bob',
-            'password' => 'aYUB1IYUadd38fl9mxAVv2',
-        ];
-        $invite->acceptInvite($details);
-        $this->assertEquals(1, $submitter->notifications->count());
-        $this->assertEquals(1, $reviewer->notifications->count());
-        $this->assertEquals(1, $review_coordinator->notifications->count());
-    }
 }
diff --git a/backend/tests/Feature/SubmissionCommentTest.php b/backend/tests/Feature/SubmissionCommentTest.php
index 571d54625..f09fcdfc1 100644
--- a/backend/tests/Feature/SubmissionCommentTest.php
+++ b/backend/tests/Feature/SubmissionCommentTest.php
@@ -3,85 +3,16 @@
 
 namespace Tests\Feature;
 
-use App\Models\InlineComment;
-use App\Models\OverallComment;
-use App\Models\StyleCriteria;
-use App\Models\Submission;
 use App\Models\User;
 use Carbon\Carbon;
 use Illuminate\Foundation\Testing\RefreshDatabase;
 use Tests\TestCase;
+use Tests\TestFactory;
 
 class SubmissionCommentTest extends TestCase
 {
     use RefreshDatabase;
-
-    /**
-     * @return Submission
-     */
-    private function createSubmission()
-    {
-        $user = User::factory()->create();
-
-        return Submission::factory()
-            ->hasAttached($user, [], 'submitters')
-            ->create();
-    }
-
-    /**
-     * @param int $id
-     * @return StyleCriteria
-     */
-    private function createStyleCriteria($id)
-    {
-        $criteria = StyleCriteria::factory()
-            ->create([
-                'name' => 'PHPUnit Criteria',
-                'publication_id' => $id,
-                'description' => 'This is a test style criteria created by PHPUnit',
-                'icon' => 'php',
-            ]);
-
-        return $criteria;
-    }
-
-    /**
-     * @param int $count
-     * @return Submission
-     */
-    private function createSubmissionWithInlineComment($count = 1)
-    {
-        $user = User::factory()->create();
-        $submission = $this->createSubmission();
-        $style_criteria = $this->createStyleCriteria($submission->publication->id);
-        InlineComment::factory()->count($count)->create([
-            'submission_id' => $submission->id,
-            'content' => 'This is some content for an inline comment created by PHPUnit.',
-            'created_by' => $user->id,
-            'updated_by' => $user->id,
-            'style_criteria' => [$style_criteria->toArray()],
-        ]);
-
-        return $submission;
-    }
-
-    /**
-     * @param int $count
-     * @return Submission
-     */
-    private function createSubmissionWithOverallComment($count = 1)
-    {
-        $user = User::factory()->create();
-        $submission = $this->createSubmission();
-        OverallComment::factory()->count($count)->create([
-            'submission_id' => $submission->id,
-            'content' => 'This is some content for an overall comment created by PHPUnit.',
-            'created_by' => $user->id,
-            'updated_by' => $user->id,
-        ]);
-
-        return $submission;
-    }
+    use TestFactory;
 
     public function testInlineCommentsAreNotRetrievedForASubmissionThatHasNone()
     {
diff --git a/backend/tests/TestFactory.php b/backend/tests/TestFactory.php
new file mode 100644
index 000000000..0583804a4
--- /dev/null
+++ b/backend/tests/TestFactory.php
@@ -0,0 +1,118 @@
+<?php
+declare(strict_types=1);
+
+namespace Tests;
+
+use App\Models\InlineComment;
+use App\Models\OverallComment;
+use App\Models\StyleCriteria;
+use App\Models\Submission;
+use App\Models\User;
+use Illuminate\Foundation\Testing\WithFaker;
+
+trait TestFactory
+{
+    use WithFaker;
+
+    /**
+     * @param int $status (default: Submission::UNDER_REVIEW)
+     * @return Submission
+     */
+    protected function createSubmission($status = Submission::UNDER_REVIEW)
+    {
+        $user = User::factory()->create();
+
+        return Submission::factory()
+            ->hasAttached($user, [], 'submitters')
+            ->create(['status' => $status]);
+    }
+
+    /**
+     * @param int $id
+     * @return StyleCriteria
+     */
+    protected function createStyleCriteria($id)
+    {
+        $criteria = StyleCriteria::factory()
+            ->create([
+                'name' => 'PHPUnit Criteria',
+                'publication_id' => $id,
+                'description' => 'This is a test style criteria created by PHPUnit',
+                'icon' => 'php',
+            ]);
+
+        return $criteria;
+    }
+
+    /**
+     * @param int $count
+     * @param User|null $user (optional)
+     * @return Submission
+     */
+    protected function createSubmissionWithInlineComment($count = 1, $user = null)
+    {
+        if ($user === null) {
+            $user = User::factory()->create();
+        }
+        $submission = $this->createSubmission();
+        $style_criteria = $this->createStyleCriteria($submission->publication->id);
+        InlineComment::factory()->count($count)->create([
+            'submission_id' => $submission->id,
+            'content' => 'This is some content for an inline comment created by PHPUnit.',
+            'created_by' => $user->id,
+            'updated_by' => $user->id,
+            'style_criteria' => [$style_criteria],
+        ]);
+
+        return $submission;
+    }
+
+    /**
+     * @param int $count
+     * @param User|null $user (optional)
+     * @return Submission
+     */
+    protected function createSubmissionWithOverallComment($count = 1, $user = null)
+    {
+        if ($user === null) {
+            $user = User::factory()->create();
+        }
+        $submission = $this->createSubmission();
+        OverallComment::factory()->count($count)->create([
+            'submission_id' => $submission->id,
+            'content' => 'This is some content for an overall comment created by PHPUnit.',
+            'created_by' => $user->id,
+            'updated_by' => $user->id,
+        ]);
+
+        return $submission;
+    }
+
+    /**
+     * Create a submission with users that have all submission-relative and publication-relative roles.
+     * Does not include Application Administrator role.
+     *
+     * @return Submission
+     */
+    protected function createSubmissionWithAllRoles(): Submission
+    {
+        $submission = $this->createSubmission();
+        $submission->submitters->first();
+
+        $users = collect();
+        for ($i = 0; $i < 4; $i++) {
+            $users->push(
+                User::factory()->create([
+                    'username' => $this->faker->unique()->userName,
+                    'email' => $this->faker->unique()->safeEmail,
+                ])
+            );
+        }
+        $submission->reviewers()->attach([$users->slice(0, 1)->first()->id]);
+        $submission->reviewCoordinators()->attach([$users->slice(1, 1)->first()->id]);
+        $submission->publication->editors()->attach([$users->slice(2, 1)->first()->id]);
+        $submission->publication->publicationAdmins()->attach([$users->slice(3, 1)->first()->id]);
+
+        return $submission;
+    }
+}
diff --git a/client/src/graphql/queries.js b/client/src/graphql/queries.js
index 2f1fc8812..559343eb5 100644
--- a/client/src/graphql/queries.js
+++ b/client/src/graphql/queries.js
@@ -48,6 +48,9 @@ export const CURRENT_USER_NOTIFICATIONS = gql`
             submission {
               title
             }
+            commentor {
+              display_label
+            }
             invitee {
               display_label
             }
diff --git a/client/src/i18n/en-US.json b/client/src/i18n/en-US.json
index 062aa8b25..73e2a037c 100644
--- a/client/src/i18n/en-US.json
+++ b/client/src/i18n/en-US.json
@@ -1028,6 +1028,26 @@
       "filter": "Filter"
     },
     "submission": {
+      "overall_comment": {
+        "added": {
+          "short": "{data_commentor_display_label} added a new overall comment to {data_submission_title}"
+        }
+      },
+      "overall_comment_reply": {
+        "added": {
+          "short": "{data_commentor_display_label} replied to an overall comment for {data_submission_title}"
+        }
+      },
+      "inline_comment": {
+        "added": {
+          "short": "{data_commentor_display_label} added a new inline comment to {data_submission_title}"
+        }
+      },
+      "inline_comment_reply": {
+        "added": {
+          "short": "{data_commentor_display_label} replied to an inline comment for {data_submission_title}"
+        }
+      },
       "invitation": {
         "review_coordinator": {
           "accepted": {
diff --git a/client/src/mappers/notification_icons.js b/client/src/mappers/notification_icons.js
index bb4a93fb4..79a3bf98b 100644
--- a/client/src/mappers/notification_icons.js
+++ b/client/src/mappers/notification_icons.js
@@ -14,6 +14,18 @@ const icons = flatten({
     revision_requested: "undo",
     archived: "inventory_2",
     deleted: "delete",
+    inline_comment: {
+      added: "chat_bubble",
+    },
+    inline_comment_reply: {
+      added: "chat_bubble",
+    },
+    overall_comment: {
+      added: "chat",
+    },
+    overall_comment_reply: {
+      added: "chat",
+    },
     invitation: {
       review_coordinator: {
         accepted: "emoji_people",