[derefr]

You can use people's comments as a (loose) proxy for their interest in a post; people who comment on something are more likely to have upvoted it (or at least consider it worthwhile to talk about, even if they never really vote on things.) You could perhaps even use Sentiment analysis, and take negative (root-level) comments as downvotes (and prune any branch below a negative comment, because it's probably an argument.)