I believe it does, but don't have any evidence to back it up. If itp volunteers, we could test by down voting his comments :)
Exactly... This effect might reinforce 'upvote'-grabbing behavior, to either not lose the ability, or regain downvote if lost.
Upvote-grabbing behavior is already rampant here, just as with any forum with point tallies attached to comments. Proof: all of the "edit: why the downvotes?" comments.