Second --and this could be quite complex-- let me, the reader, decide who and what I want to read. In other words, let automatic moderation have a light touch and let me, as a reasonably intelligent adult, decide what I want to see.
For example, an obligatory "tech"/"non-tech" tag could allow readers to choose not to see anything that isn't tech related.
I know, tag hell could be horrible. Yet, there probably exists a reasonable set of tags that could allow users to moderate their own feeds rather than having to worry about central moderation.
I could see new posts being tagged "non-tech" by default unless the poster chooses another tag. Tags could include "art", "politics", "religion", "economics", etc.
I'd keep them to a very short set, perhaps five or ten. No more. Too many tags and HN becomes something it isn't.
Within the concept of allowing the reader to shape their own feed there's the idea of "private hell banning" if you will. In other words, if I don't want to see posts from specific people that should be my prerogative, perhaps others are OK with the posts while I am not. Let me mute someone personally rather than centrally muting them as if the entire community thought exactly alike.
I know running communities is extremely hard work. I have in the past and have zero interest in doing it again. HN has really high S/N and that's why I like to read it every day. I've been guilty of adding to the noise here and there. I'm only human. I have tried to self correct when that's happened, mostly by tying to stay away from non-tech threads.