Disagree. Reading these comments, especially when they relate to specific technologies, I have come across numerous systems, resources and techniques that I have gone on to use in practice. I'll just take this opportunity to say a quiet 'thank-you' to their respective authors.
For example, you see somebody posting what you know is a big misconception. You spend time and effort educating and clearing it up. Even if you succeed, you soon run out of patience - you reached a hundred people, 5 of whom cared and will remember. However, there are a few hundred million left in the world who still have that misconception, and there still are way more daily conversations and blog posts where the misconception is spread. You on the other hand spent half an hour education a handful of people. How long until you ignore comments you know are wrong and just shrug and go on with your life?
Answering a specific one-time question by pointing to some resource or project is easy enough in comparison. I did not mean to imply that all comments are always useless. I did not think it would be necessary to point that out. See, that's another problem, somebody always comes up with an interpretation of what you write that will make you spend even more time to clarify because you never thought that interpretation would happen.
Could comments be assigned some big weight that has the effect of the comment staying around high enough to clear the misconception?
Could each thread be allowed only a finite number of comments or words, to not disperse attention, with lower quality comments forced to disappear?
Could there be a fool-proof mechanism to force comments you know are wrong to disappear?
If a new site like HN or Reddit showed up, how would would like it work? I ask because I'm toying with the idea of one. Thoughtful beta users get in touch.