[badbug]

The upvote is an implicit down vote for other things.

I think you need two things. First an upvote/downvote so that users can express their agree/disagree. This value wouldn't necessarily effect the visibility of the content. Second, a sort of budget system where users can trade earned karma to classify an items "quality".

I think this would lead to a system where you would spend your karma on the communities you care/know/like the most. If I were, for example, a blind apple hater, the upvote/dowmvote makes it easy to downvote apple content or upvotecother content to push it down the page. But I may be more inclined to save my karma for promting Android content instead.