I've spent a lot of time thinking about this, because I had to make a decision as to whether or not to be a part of this "community." Aside from some speech-and-debate oriented forums in high school, I've stayed away from online communities. They just don't seem to have high quality discussions, even at places where tech thrives, like xkcd. I suppose I'm lucky to have a job where I get to work with a lot of stimulating and highly intelligent people, with whom I can have conversations that last several days, so maybe my perspective is somewhat anomalous, but I doubt it. In any case, I stumbled upon paulgraham.com a few months ago, and what I enjoyed most in his essays was the reserved, focused quality, so I figured a forum/news site run by him might be interesting. I've also had an interest in open/accessible science via web-based applications, and becoming a good enough coder to write some of what I do on a Cray machine at work [1]. I am not a hacker. I learned Visual Basic in high school, and can get around basic web design/javascript/rails tutorials and stat scripting languages we use at work like R and Matlab, install Ubuntu and use Vim daily. This seemed like a good place to learn better techniques.
I've learned a lot, and I won't go on about that. Many of the comments have been thoughtful and informative, particularly the ones that point to relevant places to get more information (I've noticed user Joakal does this a lot [2]), or the ones that disagree substantively.
But the most frustrating kind of comment I've encountered on this site isn't meanness, or blatant stupidity, but the Hard-Not-To-UpVote kind. Most people can tell a troll, and most trolls get down-voted to the point of white-out. Most stupid one-line jokes get voted to the bottom of the page as well, or just ignored. Today's discussion[3] was extremely embarrassing, so much so that if I'd seen that discussion first I might never have joined the site, but the meanness was not among the most up-voted comments, and even though there were a some annoying individuals who felt the need to prove how unremarkable someone was, most were rather positive. And the rest of the community rallied around upvoting jaquesm's comment, and downvoting the inappropriate ones to oblivion (though not soon enough).
One unfortunate thing I've noticed: a lot of the very popular comments are sometimes of a "fluffy" quality. I'm a "scientist" and I get to sift through a lot of hype on a daily basis; what I appreciate most are focused rational arguments, even if I ultimately disagree; I don't like fluff, even if I've used it from time to time, and certainly I've fallen for it. I remember reading a few months ago a great passage in a PG essay:
The most dangerous thing for the frontpage is stuff that's too easy to upvote. If someone proves a new theorem, it takes some work by the reader to decide whether or not to upvote it. An amusing cartoon takes less. A rant with a rallying cry as the title takes zero, because people vote it up without even reading it.
Hence what I call the Fluff Principle: on a user-voted news site, the links that are easiest to judge will take over unless you take specific measures to prevent it.[4]
I think this applies to some comments I see here (maybe some comments I've made). Quickly shot off, and easy to judge, the ones that make you feel guilty not upticking. I don't know what to do about it - I have upvoted some comments of dubious quality because it's hard not to, but what I appreciate most is substantive disagreement. My favorite things to upvote are comments that disagree with me, even if my mind isn't ultimately changed. Comments I can't stand (and feel guilty for making at times) are the ones that say "great point!" or offer an emotionally charged appeal with nothing interesting or unique. I can't say my perspective is unique here, but I do think it's an unsolved problem.
PG actually submitted an Ask HN several months ago regarding what you mention[5]. I'm curious if anything came of that. I don't know how to make it work. In real life, when people I have discussions with consistently detract from the value, they get left out to some extent, or if I'm in a group where fluffy comments are prioritized, I leave, and eat lunch with other people. I have no idea how to make this work on the internet. This would be sad, because I don't know anywhere else on the internet that has this level of discussion.
[1] http://beagle.ci.uchicago.edu/ [3] http://news.ycombinator.com/item?id=3466925 [2] http://www.hnsearch.com/search#request/all&q=joakal [4] http://www.paulgraham.com/hackernews.html [5] http://news.ycombinator.com/item?id=2403696