I often find myself informing the newcomers about the comment @replies, since otherwise the comments they write (when trying to reply to someone) often remain unnoticed due to lack of notifications.
I propose adding an automatic message explaining how the reply system works.
Something like this:
When the user tries to post a comment, if:
- Nobody would get a notification unless they
- They're commenting under their own post, and
- At least two other users have commented on the same post (if there was only one user, they will get notified regardless; if there were no other users, we assume that the comment is not directed at anyone in particular), and
- The user hasn't dismissed this notification before, and
- (optionally) They have <N rep (or any other criteria to avoid showing it to existing long-time users).
Then show following text next to the comment textbox:
When replying to other users, begin your comment with
@username, otherwise they won't get notified. (more details)
I'm not a native speaker, so the message wording can probably be improved.