I'd note that one of the people who's behaviour was exactly the kind of behaviour that should be discouraged ('I hate to be the guy') has very overall high score and quite high avg score.

I think conflating comment score and article submission score is a mistake because of this kind of thing.

I do not think this would work very well. I can't speak for others' habits, but my posting comes in bursts. Usually I post rather infrequently--just answering some comment or espousing my views on some moderately interesting subject. However, when I find something really interesting (like a Haskell article :)), I am likely to post in rapid succession.

However, I think that my posts on such subjects are the most beneficial for the site--they're the ones where I have a decent amount of knowledge and direct experience; I am much more likely to contribute something insightful on a CS article than on a sociology one, for example. Rate-limiting would make it harder for me to post about my strongest subjects without changing how I post about random articles.

Perhaps one that takes into account the categories you do post in and have a high karma for?

Then you have the nontrivial problem of trying to categorize all the posts.