A few years ago, posting on HN felt like posting to a small community. Reputation and civility seemed to matter a lot. When people posted something offensive or rude, they were sanctioned to the point that they would often delete the offending comment. (I remember deleting a comment I made on an old account merely because, without tone, it seemed inflammatory; I felt compelled to delete it even though it had no malicious intent because it damaged the conversation.)

Now, I think it has become too large and feels anonymous. Posting something offensive has no cost because it doesn't feel like a "know your neighbor"-type community anymore. The costs imposed by karma seem to be less significant. I even think that if you post a rude or ideologically motivated comment, there are other rude people who will agree with you, attenuating the negative signal.

The HN is turning to reddit mime is genuine. I think it's just a consequence of having a very large community. Although a lot of HNers may disagree, I think the herd must be culled. I'd be happier of participation was limited. If I was the benevolent dictator, I'd collect a list of people whose contributions are most valuable and remove everyone else. Then, give those high-signal / low-noise contributors the ability to invite other people. Continue to have all content publicly readable, but ration the writes.

(Disclaimer: Although I have many doubts, I do believe it is possible to have an HN-scale community that remains civil; however, without the data, I'm not very comfortable just enumerating implementation ideas.)