plausible code solutions for this?
I really don't like the idea of "legislating morality", i.e. building community norms of behavior into the structure of the site (such as, for example, taking away the ability to delete comments because of widespread disapproval of the way this feature has been used by some [Roko]).
Having said that, I'm really surprised that no one has suggested the most obvious "fix", which would be to disallow voting from user pages. (I don't necessarily endorse implementing this, but if something is going to be "done", this seems the least harmful.)
But I think voting from the user page has a 'legitimate' purpose- in a way that downvoting every contribution from a user over the last 6 months doesn't. I know I've seen insightful comments and thought "Hey, komponisto's contribution on this subject seems sharp, lets see what else he's written" and then proceeded to vote up a bunch of comments from the user page. Voting down comments this way seems somewhat reasonable, too (most obviously in the case of clear trolling).
As for "legislating morality" obviously not every misuse of the si...
People who go back and downvote every post or comment a Less Wrong user has ever made, please, stop doing that. It's a clever way to pull information cascades in your direction but it is clearly an abuse of the content filtering system. It's also highly dishonorable. If you truly must use such tactics then downvoting a few of your enemy's top level posts is much less evil; your enemy loses the karma and takes the hint without your severely biasing the public perception of Less Wrong's discourse.
(I just lost over 200 karma in a few minutes and that'll probably continue for awhile. This happens to me every few weeks. Edit: I mean it's been happening every few weeks for a few months for a total of only three or four. Between 400 and 700 karma lost total I think? I don't mean to overstate the problem.)