I thought about this quite a bit. I don't think I want downvoting. And I don't want effectless upvoting. The way it is right now is that you can add a paper to your library, and it will then feed into your personal SVM as a positive example of papers you like to see more of. Adding paper to your library as a type of paper you like to see more of effectively counts as an "up vote", and is what is sorted by when you go to the "top" tab.