Wouldn't it be a good idea to silently hide the posts from everyone except the troll. Now he (or she) has been public outed he'll probably try again with a new set of accounts.
The thing is, Hacker News has too small an audience to make gaming very worthwhile. I think that clamping down once is good enough to send the message across. I'd hope so, anyway, since it takes a lot of effort to get to the point where you can vote things up and down.
