I have “turned off” the ability to use html in my comments. Hopefully, this will cut down on some of the comment spam I get.
I use and love MT-Blacklist, but until you teach it what to block you still have to go through and clean your blog (i.e. remove the damn spam from your comments), then add the patterns into MT-Blacklist.
Maybe this move will cut the amount of spam I get in the first place.