Actually, I find it interesting how HN incentivizes good behavior with their karma system. Yes, HN discussions are most of the time not about social values, but nevertheless I found that it changed me a bit, so that I think more about how to write my comments.

So what I like about the system, is that (for experienced users) down voting is allowed and that a down voted comment is getting less attention (less karma damage, less reader damage) and that is getting faded out (so while reading comments you can quickly skip the bad comments).

That way, you don't have to be afraid of writing a bad comment accidentally, because the system takes care of it, but when you write one you can see that that less people are reading it compared to a good one. I just wish down voting would require writing an answer. Nothing is more frustrating than a down voted comment when you do not know why people didn't like it.

Over the past years, I found that other readers like comments which tell them something new and insightful about the topic. Links for further reading and as references for opinions are also appreciated.