Quality is something hard to measure, we're in a community, so I think that the quality of a thread is given by the number of points it has, not by the number of comments.
The number of comments just mean that people have something to say about an specific thread.
I disagree with your metric for measuring quality -- all one has to do is look at reddit or digg to see that it fails. Of course, quality is in the eye of the beholder. I'm sure there are plenty of things who think that reddit or digg are the highest quality news sites out there.
Hmm... That's an interesting question. How do we actually measure quality?
I agree with you, for me the number of points a thread has is just a measure of how many people in our community think it's an interesting topic.
About the quality of the thread, well, as you said, quality is in the eye of the beholder, for example, the thread that pg is showing as an example, (http://news.ycombinator.com/item?id=106893) is a funny and interesting one for me.
How we actually measure quality?... Hmmm, that would make a great startup right?
Some articles don't leave much to comment on. If there some new discovery, I think it's actually better that there aren't 15 comments saying "Cool!" and "Awesome!". I think that the comments that are made are generally high quality, so the signal to noise ratio is still high.
While I totally agree, I read YC news as much for the comments as for links, hoping to find some interesting or illuminating angle on the article - which I often do.
And I really resist the urge to post comments that don't give a perspective, an opinion, or a fact. Often I really want to write a "yeah cool" or "LOL" comment, but I don't. There are plenty of those elsewhere on the net.
The whole point of being able to upvote, in my opinion, is to be able to say, "yeah cool" or "LOL" without creating a lot of noise. Our instincts may want our name to show up saying "I AGREE WITH THIS", but once you get used to it, it's not such a big hurdle to get over.
This seems like a generalization of Warnock's Dilemma (paraphrased, "if a forum post has no replies, it cannot be determined whether it is because it is so smart and concise that it cannot be enhanced, or because it is too stupid to warrant comment").
It's an information problem. We can determine from comment contents what about an article warranted feedback, but we cannot determine anything from the lack of comment (i.e. the one that never gets posted).
That sounds kind of like voting. I have heard people say, "Don't vote, you're just validating a rigged system." At the same time, others equate low voter turnout with general well-being; that is, they're not voting because their life is good and not likely to change much either way. Again, it's an information problem.
You weren't around last time applications opened for YC, were you? ;) The entire site seems to sort of shut down. Submissions drop off, commenting becomes practically non existent. The silence is very surreal.
The increase in people who think such links are cool to submit and vote up is the most direct sign of declining quality. This site has switched from startup news to meta discussion about itself.
RSS feed items don't have a link that takes directly to the comment page. I am too lazy to go to the main page, search for the entry and post a comment.
In any case, the number of comments on a link doesn't seem very highly correlated with its quality: http://news.ycombinator.com/item?id=106893