Don't send notifications for moderator action posts

app/models/post_alert_observer.rb

@@ -63,8 +63,8 @@ class PostAlertObserver < ActiveRecord::Observer
       post.topic.all_allowed_users.reject{ |a| a.id == post.user_id }.each do |a|
         create_notification(a, Notification.types[:private_message], post)
       end
-    else
+    elsif post.post_type != Post.types[:moderator_action]
-      # If it's not a private message, notify the users
+      # If it's not a private message and it's not an automatic post caused by a moderator action, notify the users
       notify_post_users(post)
     end
   end

spec/models/post_alert_observer_spec.rb

@@ -108,4 +108,16 @@ describe PostAlertObserver do
 
   end
 
+  context 'moderator action post' do
+    let(:user) { Fabricate(:user) }
+    let(:first_post) { Fabricate(:post, user: user, raw: 'A useless post for you.')}
+    let(:topic) { first_post.topic }
+
+    it 'should not notify anyone' do
+      expect {
+        Fabricate(:post, topic: topic, raw: 'This topic is CLOSED', post_type: Post.types[:moderator_action])
+      }.to_not change { Notification.count }
+    end
+  end
+
 end