It happens when someone votes in a poll even if they don't leave a comment (that would be the reason for the "Vote" thread). The other reason it happens is if someone hits the "Bump Thread" button under the Thread Tools menu. I have a feeling someone is sick of the continuous stream of Wipe New threads so they're bumping them all to the top of the list so people see how ridiculous it is.

Dub? Sue? Any other troublemakers out there?