Rebecca Rosen makes the good observation that after a decade's experience, "Internet comments continue to be terrible":
So many things about the Internet have become pretty awesome over the past decade or so, but there is one thing, however, that remains dysfunctional: comments. They continue to be terrible, and it's not only because of trolls and morons. Internet comments are hard to read and harder to engage with. Even in places with smart, thoughtful readers, the comment sections tend to be more like lists of unconnected ideas than genuine conversations. The problem is simply that it's hard to build a system that allows for smart ongoing conversations among large groups of people. It's a harder problem, fundamentally, than how to present and create good content.
I don't have time to get sidetracked by this at the moment, but it's an interesting question: why should something that in theory is so simple be so hard to do well? What's the hidden complexity that comment thread designers miss?