Possible Duplicate:
How do comment @replies work?
If I mention someone in my comment with @user and that user is not part of the discussion, will he/she receive the notification?
Possible Duplicate:
How do comment @replies work?
If I mention someone in my comment with @user and that user is not part of the discussion, will he/she receive the notification?
No, they won't.
Only the people who edited the post and commented on it will be notified.
See How do comment @replies work? for details.
Unless:
More info: How do comment @replies work?