FYI what triggers the inbox doesn't match what triggers the envelope, but I'll only answer RE the inbox.
- comments on a question/answer of mine;
- comments on someone's question, directed at me (@name);
Yes, but only if you've done at least one of:
- Made a previous comment against that question or answer.
- Previously edited that question or answer.
- same as the above, but if I've never even read that question;
No, for the reasons stated on the previous point.
- mention of my @name in a chat room I've never been to;
Don't know for sure, but I think not...
- partial mention of mine, i.e. @bruce instead of @bruce connor?
Assuming the request meets the relevant criteria above, Yes (except possibly on Chat, which needs full names I believe).
The @reply system requires only three letters to match (so @DMA would hit me), and only considers the name given up to the first space. It will ping the person who's name matches, and in the event of multiple possibilities will only ping the person who's activity was the most recent.
- What OS? - John Smith 15mins ago
- Should this be on SO? - John Fredrickson 13mins ago
- @John Smith, I'm on Win7. - OP 5mins ago
Here, the inbox ping will go to John Fredrickson, because they were the most recent user who matches "John" (because the system doesn't consider spaces, the Smith is ignored). Note that (as per the comments) you could use @JohnSmith to target the correct person.
Additional Causes (that you didn't mention)
- New answers against a question you created.
- You cannot use two @name calls in a single comment - only the first is considered.