Technology can make community management easier. Better algorithms and visual design and so on can improve the way that a community polices itself. But, I think eventually you'll run into vanishing returns from that kind of stuff. (I don't have any good science for this, but I've been spending too much time online since the dial-up BBS days, and community development is one of my interests.)
Eventually every community needs one or more managers, or gardeners (http://lesswrong.com/lw/c1/wellkept_gardens_die_by_pacifism/) -- people who have been around a long time, who embody the "spirit" of the site, and who have, not absolute, but special influence on the community. (RiderOfGiraffes immediately comes to mind; I really wish he was still around.)
This is absolutely analogous to Google attempting to avoid customer service completely by piling on more and more automated systems. While those systems help, they can't yet replace an actual customer service department -- and I think the frequent complaints from people who've been impacted by Google's lack of customer service bears this out.
I like some of the suggestions in this post, but I don't think that they can resolve the main issue with HN at the moment: it has grown to a size which needs one or more community managers.
There are some architectural issues too. I think the current trend in online forums, where new things are always better than good things, is ultimately a step backwards in terms of encouraging thoughtful discussion (http://www.robsheldon.com/conversations-online/). If a really interesting item comes up on HN that requires, say, a solid hour to compose a thoughtful response -- something very technical that would benefit from some number crunching -- there is very little motivation to commit the time to write that response. By the time it's written and posted, the site has moved on to the next new thing. However, the first person to respond to an item with a quick, witty, or snarky response gets rewarded with lots of attention.
And that is a problem that can not be resolved by any of the suggestions so far.