We’ve had a troll infestation lately. I know perfectly well who it is, the spiteful jerk, but with the infinite variety of anonymous IPs out there, there’s no way to have a completely open comment system and keep him out by banning IPs.
So there are two choices: full moderation (which would pretty much ruin the commenting flow entirely) or making everyone register with WordPress to comment.
I’m going to go with the latter. It shouldn’t be a particularly onerous requirement, and it does mean that trolls will really have their work cut out for them. Let’s see how that goes for a while.