What I already told Esten on twitter: He outlines some aspects of a method to keep the 'good contributors' engaged, even if the community grows, by highlighting their contributions. What interests me is how to scale these good comments without excessive moderation. And also, even on sites that have moderation available over time there's again and again this boom-bust cycle, where comments start out being really insightful when the community is small, which attracts more people which brings down the quality of comments, making people less interested in high quality commentary (and also the general audience less interested in the comments at all).

I think limiting the number of contributors is interesting, but I wouldn't limit the ability to reach a big audience per se. Precisely the possibility to reach an audience entices high-quality comments. Possibly part of the real challenge is actually to keep the non-commenting audience interested in the comments.

So maybe it's about limiting the number of contributor-slots available in any given situation, and then of course think of a non karma-whoric way of assigning those slots... hmm :) Maybe even make it random, so anybody can get one of those slots, so create a sense of urgency not to blow that chance. Might work in some situations.