Didn't use it. In fact I lost access to it (I was rather pissed off with this whole enterprise and changed password to something I don't remember). I didn't downvote this guy, my guess is one of 14 people that upvoted my retort to his post did, possibly after my retort got deleted and his remark did not get deleted.

Still can't downvote. The maximum number of downvotes you can give is 4 times your karma, which is zero with zero karma. So you have to keep gaining karma in order to keep downvoting, and a karmassassination would take a while to save up for.