Add ability for users to ignore certain other users' posts
The above user spammed/overposted many many times, and it would be nice if I just didn't see his/her posts. =) A more complicated solution would be to have Hide/Unhide on a per question basis; almost the opposite of favorites, without any karma penalty.
When no admin is around to moderate, everyone is at the mercy of spammers. Also, the people who downvote such users only get penalized themselves since said user can't have his karma fall below 1. Perhaps a downvote should not cost the voter any karma if the target user is below a threshold, say 10? (Perhaps it already is, I haven't downvoted yet.)