Oh wow, I'm so happy I'm not the only one thinking this. I noticed this transition over the past few years on these forums and I even commented about it in the past.
It is the path of things on the internet that are interesting and then become popular. Same for Usenet :) Kuro5hin escaped by becoming uninteresting. Our descendants may find a solution.
Things change over time. Also note that HN used to be over-run by libertarians that would make Ayn blush. Kuro5hin escaped by dying. There is lobsters, but it has almost zero discussion and overly focuses on "the rules".
I think norms are better and more powerful. Be the norm you would like to see in the world.
I should qualify my statement as I get voted down into oblivion. Hn still has higher quality comments and I'd ever seen it slashdot. However those high value comments usually come on particular subjects that lie within the hn community's zone of expertise. However for political topics or for science articles, hn comments usually lack expertise or neutrality. They're all falls into whether hn thinks of itself more as a repository of expertise or a forum for individuals to discuss topics where those individuals have expertise in some topic ie a professional which by and large the community is composed. Please excuse any strange typos I am voice typing this as I walk.