Depends how you tie it to a real person, if the real person has to give up something to sell an identity, make the cost of selling it high.

Problem is also how do you tell the downvotes because their new post is bad from the downvotes because you're in a gang that's attacking someone. Your downvotes have to be scaled with your own reputation, as do your upvotes. And downvotes found to be part of a conspiracy have to be cancelled and affect the conspirator's reputation