I read jalopnik from time to time, and I can't say I've noticed that the comment quality has been anything special.

The best comment model I've seen is the NYTimes, which combines moderation and featured comments (the user recommended comments are too heavily biased towards what was posted first to be useful).

Posted recently, "How to correctly sort by average rating":

http://www.evanmiller.org/how-not-to-sort-by-average-rating....

From the headline, I thought this meant that making all comments harder to see will increase quality.

In fact, the proposition is that rewarding good commenters with higher visibility will increase quality. Makes sense, and it's nice to see some quasi-empirical evidence for it.

shouldn't this graph be controlled for traffic? if traffic has grown, that's probably where a lot of the extra comments came from.

The graph is designed to illustrate that heavily controlling comments still generates a lot of comments.

That said, it would be interesting to have a graph that shows the engagement rate for users; something like Comments for every 1 Million page views.