The subject line in email notifications contains the username of the person posting, so the subject keeps changing whenever someone replies, and this breaks Gmail's conversation functionality (see: http://mail.google.com/support/bin/answer.py?hl=en&answer=5900
This has been bugging me for a while now. Conversations are much easier to manage than pages of emails. I've asked about this before, but nothing was done. The body of the message contains the thread title, but it should be in the subject line, and the username should be in the body instead of the subject. Please switch them.