Let me say that a little more clearly:
Someone might argue that "the commentariat on LesserWrong are a group of people who are more nitpicky and less helpful than my friends on Facebook". I'm not sure if this is a strawman.
But I'd like to propose, instead, that the comments being posted on LesserWrong are the result of people responding to incentives imposed by the karma system. For whatever reason, it appears that these incentives are leading people to post nitpicky and unhelpful comments. Improving the karma system might fix the incentives.
You've suggested elsewhere that the post owner might move irrelevant comments to an "off-topic" section, and that's a good way to deal with off-topic comments. But what if a comment is directly replying to my post, but I just sort of feel like it's nitpicky and unhelpful? I could mark it as "off-topic", but this wouldn't be strictly accurate.
Instead, I'd propose letting the post owner mark certain comments as "helpful", which would be worth +10 karma, or would double the value of all karma received, or it would sort those posts to the top where more people would see them, or something.
This behavior of writing a post and getting unhelpful comments: is it something that can be changed by tweaking the karma system?
Like, right now, if I read a post and think of a true-but-unhelpful objection, maybe I post the objection in the hope of getting upvotes.
But maybe if you make the post author's upvotes worth more than upvotes by random schmoes, then I optimize more for posting things the post author will like?
There are a whole lot of social networks out there, each with its own rules and karma system. I wonder if anyone has done a survey of what works and what doesn't?
More specifically: for the past few years I've had an account at rpg.stackexchange.com. I've found that this site performs its function remarkably well. When I read questions on this site, I feel motivated to write clear, helpful, somewhat-researched answers.
There are lots of other social networks. Reddit comes immediately to mind. I think slashdot has put a lot of effort into their system. And of course there's facebook and twitter and tumblr. I don't know much about these sites, except that I find them sort of irritating, particularly in the comments section. But probably someone who uses those sites more would have more to say.
If we're really dedicated to figuring out how to do comments properly, it seems like we should start by doing a survey of what already exists.