BuddyPress.org

Had the same problem. This was covered by Burt and myself a few days ago, but it comes down to the fact that everything in your install is fine, but not in your functions.php. The reason comments aren’t showing up is because it’s actually loading index.php instead of single.php.

If you copy the latest functions.php over from RC1 into your template, it should all come back to you. If you made any custom edits to that file, be sure to move them over of course.