Since when do comments on questions and answers show up on the main page? I don't mean that they can be read there, but that the question is bumped up on the main page, and that the last activity noted on the right side below the title is the comment (or, rather, the time of the comment and the name and rep score of the commenter - "3 h ago JoeYodeya 1205", for example).
What you're seeing may be an instance of an answer that was converted by a mod into a comment. The post was bumped when the user posted the answer, but all you see now is the comment, as the answer in its original form was deleted and is invisible to users with less than 10K rep.
2Urgh, still not used to not seeing deleted posts. Thanks!– Seth JMay 31, 2012 at 17:22
2@SethJ Mazel Tov on your recent 10K! I just noticed.– Double AA ModJul 12, 2012 at 3:43
@DoubleAA, I take it back. I just saw a deleted answer on an old question. But I still thank you (I don't take that part back).– Seth JJul 12, 2012 at 3:59
@SethJ Here are the tools. judaism.stackexchange.com/…– Double AA ModJul 12, 2012 at 3:59