I was going to comment last night on the post on how to sleep better in the Summer, but I didn't in hopes that sort of thing would stop itself. But all-in-all that sort of stuff doesn't belong on Hacker News, after all the site is Hacker News.
In the interests of full disclosure, I was the one who submitted the "How to Sleep Comfortably on a Hot Night" article. Yes, it's not topical. However, I'm not ashamed! I thought it was interesting, and clearly so did the 44 other people who upvoted it.
I'm quite pleased with the community that's developed here, who are discriminating enough to pick out many articles I find interesting.
However, HN could definitely be improved, so that people who are only interested in certain topics (such as only computer/hacking related articles) or not interested in other topics (such as off-topic, or political, or venture capitalist articles) could more easily filter through what's becoming a firehydrant of links.
I think the best way to do this is by implementing tags.
And you can say that Hacker News will stay pure or whatever but this is exactly how things began with other sites and then slowly but surely things became less and less relevant. I do think that it will take quite some time before Hacker News gets that way but I'd rather be strict now and nip it in the bud before regretting it later.
With the analogy of tags I would say that if you had the two most basic tags: "hacker-related" (programming, science, tech and related fields) or "non-hacker-related" (ie. sleep habits) Then I would only have hacker-related tagged material here.
Now I realize that in the case of Digg they did purposely branch out to expand their community. And I doubt pg would do the same. Thus the speed at which Hacker News would descend in quality would be much slower, but in my mind it's not a sense of speed it's a sense of direction. And right now Hacker News is descending from the direction and the kind quality we had.
If I could be so bold as to take a guess at what you mean, it seems you're suggesting that the HN community submit only topical links.
I think that suggestion will generally simply be ignored by those people who want to (for whatever reason) submit non-topical links because only a small fraction of HN submitters will even read your suggestion, and most of those that read it aren't going to care (or they wouldn't have submitted off-topic links in the first place).
In order to reach all submitters, we could have some sort of global notice reminding everyone to only submit topical links. Maybe a stern and clearly worded warning on the submission page itself.
But say we do that and people continue to submit and upvote off-topic links. In my opinion, this is precisely what's going to happen. So then what?
I think there is no solution to keeping HN pure short of having the site be moderated by people dedicated to keeping it pure. But clearly that's not the model HN wants to pursue.
As long as HN is self-moderating it will not stay pure, and the more popular it gets, the further away from purity it will drift (witness what happened to Slashdot and Kuro5hin).
So, given that HN is not and probably will not stay pure, how can we improve the situation? I think the solution is clear: tags. Tags will let each reader more easily focus on what they find interesting, no matter how "impure" the site gets. It's an easy solution and one that should scale pretty well.