As discussed repeatedly already, the following scenario happens a thousand times every day on Stack Overflow:
- Newbie OP asks question
- User posts comment asking for clarification
- Newbie OP posts clarifying reply but doesn't add @username
- User never finds out that a reply has been made.
Can't "Facebook style" notification (that is, notification on all replies in comment threads I've contributed to, without the need for @username) be introduced at least for comments to the actual question? That would probably solve 99% of the problem.
Alternatively, as @Arjan suggests, limit this to comments from the OP.
Using the favourites function for keeping track of crappy questions sucks. So does manually crawling through the own "activity" page. Why does the potential answerer have to go through this?