The karma thresholds and losing karma on downvotes also helps a lot to sustain the culture. Having to gain at least a bit of karma before being allowed to upvot

The karma thresholds and losing karma on downvotes also helps a lot to sustain the culture. Having to gain at least a bit of karma before being allowed to upvote yourself is hard, if unthoughtful comments are downvoted by the community. And gaining these first (i think it was) 500 karma to downvote yourself can take a long time and makes you instill HN culture. The discussion culture is what makes me read HN nearly every day. The comments are often more interesting than the articles themselves.