The biggest thing that jumped out at me was that signal vs. noise is the most important criteria for a service to be used, but what a lot of analyses miss is that you have to interpret something before you can decide if it is a signal or not, and that interpretation is by definition individual. I think this is what happens a lot of the time when people complain about a site becoming "too big", idealizing the past when the "riff-raff" hadn't gotten in. But I think this is mistaken for the same reason that generational rants about the fecklessness of the youth are mistaken, ie Occam's razor says that we are probably not all Nietzschean superman vs newcomer's being idiots, but instead we are probably more or less equal. What is happening instead is that as a larger group comes to a site, a larger number of interests and opinions come as well. And what I interpret as noise, what those people interpret as signal.
By this I mean that if a large number of art enthusiasts joined HN and started posting a bunch of articles on art history, I would probably not be interested as my interests lie mostly in the tech arena. Let's further posit that these art enthusiasts are pretty competent in their field and so 90% of what they post is "worthwhile" in some vague broad sense. This influx might actually increase the overall signal to noise content on HN, while for me it would appear as though HN is getting swamped with crap. This is why people talk about trying to keep things exclusive or invite-only, we are trying to keep the broader perspectives involved aligned with our own, so as to not get swamped by noise from perspectives with no overlap to our own.
And this I think is the root of a bunch of the complaints about politics being posted to HN. While I may shrug off art history posts, politics is another word for how we organize ourselves to live together and as such as is much more personal and much more important. And so people's personal reactions to politics they disagree with, and by extension political stories they disagree with, is much more aggressive. So even a small amount of political discourse that you disagree with can seem intolerable.
So what is the solution? Well if I had that, I would be rich, but I do have a few ideas. The first is that reddit is trying to solve the signal interpretation issue with subreddits, wherein people can manually opt in to streams of article that they believe will be signals to them, while blocking out all streams that they will personally interpret as noise. But this still relies on manual intervention as well as discovery, along with user moderation to maintain the signal. And why do we still do things manually when we have computers!? :)
So one area that I think is really overlooked is that right now every site interprets "down/up votes" and flagging as me speaking about what I think is useful for the community. But this is just my interpretation and so aren't I really expressing my own preferences here? Why aren't sites taking my history of voting/flagging and running some machine learning on the the contents of the stories associated with that history to try to tease out patterns in what I appear to approve and disapprove of?
For myself personally I wouldn't care if I ever read another article on coffescript or libertarian politics. But if I downvote those things here on HN I am making a judgement on what I think is best for the rest of the community, and who am I to make that choice? Why can't the HN front-page see that I'm logged, look at my voting history, and just remove those stories from my view of the front page? Ta da, automatic subreddits. I think a lot of work could be done in interpreting my actions in voting/downvoting on a much more personal level, rather that looking at them in a democratic fashion.
Of course, the big unanswered question with the above is how do we avoid the echo-chamber effect, and what about that rare story on coffeescript I might actually want to see? But for now, I think the above would be a good first step, with some sort of bail-out possible if I want to "broaden" my perspective. And anyway, aren't we all trying to create an echo-chamber anyway by coming to HN (aka hacker focused stories)? So what could it hurt to make things a bit more personalized for myself?