That's really cool. For some reason, the ranking changes every time I click on the same category. Edit: I just realised it's probably because the position of users who have the same score is randomised.
Libertatea's score was computed on a very low number of comments so it may contain large errors, pergaps we should remove him/her or show a warning there...
Also, why is Libertatea (https://news.ycombinator.com/threads?id=Libertatea) ranking so high in many categories and yet he only has 5 posts?