perhaps upvotes and downvotes can be subtly weighed by karma? This would give proven contributors more trust. In the case of job posts, it would enlist them in zapping the spam they recognise month after month?

And beyond that, beyond applicability to job posts, perhaps voting can be a collaborative filtering bubble instead of absolutes? This makes spammers and voting rings end up in an echo chamber? And perhaps for normal posts instead of there being an early top level comment that gets to the top and stays there and monopolises the conversation, you get more variety and people more easily find the conversation they come for?