I've been retributively downvoted by one or two people over the past week and have lost about 110 karma. (Though I don't think I posted in the thread linked by the OP.) I agree that we need a system in place to correct and/or prevent abuses of the karma system.
At bare minimum, I think that LW should have a private log of users' up-vote/down-vote history accessible by the moderators. If someone complains of karma-assassination or the like, moderators could review the log and take appropriate action.
I'd support having such a log for administrators, although I find it likely there already exists such a thing as LW does keep track of every upvote and downvote of every user on every post/comment they up/downvote.
I would only want them to take "appropriate action" if appropriate means announcing clearly any new policy and preferably automating that policy. I do not think an unannounced one off "you are a bad person because you downvoted whoever 7 times thursday so we are X'ing you" without putting some automation and/or warning in place is appropriate.
Several people posted recently in a thread on women, mostly espousing feminist views - only to find that someone had declined to respond to their post, but instead browsed their history and downvoted every single comment or article they had ever posted.
I have two questions:
1. Why would you come to a site like this and pollute the karma system? How does it make you smarter? How does it make anyone else on the site smarter?
2. What would be a good technical workaround? In my mind, some system that detects mass-downvoting and flags a user for review would be preferable, but what should happen then? Should the system be more lenient to higher-karma posters? Who should perform the review process? What should be done with those whom the reviewer ascertains are abusing the karma system? I would prefer some kind of lesson that is more corrective than retributive - it seems to me that people who would perform this behavior are exactly the sort of people who need some of the lessons that this site provides. Any ideas?