BuddyPress Activity Comment Notifier plugin emulates the facebook style notification for the comments made on user updates. It will show the notification to a user in following scenario
- When a user has an update and someone else comments on it
- When a user comments on someone’s update and other users also comment on that update, all the users are notified
Does it sends a mail notification?
No, It does not. It just shows the notification in the drop down when a user is logged in.