In his "How to Disagree" article, Paul Graham presents some insightful thoughts about discussion on the web. He proposes a 6-level "disagreement hierarchy" to identify and classify the different types of arguments made, from DH1 = "name calling" to DH6 = "refuting the central point". It reminds me a bit of the work of Karl Popper.

Imagine taking this one step further and turning it into a mechanism to improve blog / wiki / forum discussions: people can tag/vote on each comment to qualify it as one of the DH1..DH6 categories. A rule could be that each person gets associated with say the average voting result, and that a person cannot tag any other comment above his/her own "level" (or perhaps a single step above). The reasoning being that only people considered able to argue on a high level would be allowed to tag other comments as being on a similar level.

With such a system, one could then cut-off low-class entries when going through a lengthy discussion thread. Quoting one of the last paragraphs in the article:

But the greatest benefit of disagreeing well is not just that it will make conversations better, but that it will make the people who have them happier. If you study conversations, you find there is a lot more meanness down in DH1 than up in DH6. You don't have to be mean when you have a real point to make. In fact, you don't want to. If you have something real to say, being mean just gets in the way

I think it would make discussions far more interesting, particularly controversial ones...