Flip side is that users who comment a lot on popular stories but don't post much tend to get overcounted. My karma/post is like 25-30, but only because I get the majority of my karma from comments. My posts themselves average like 5 points.
I've picked up literally 100 karma in the last week or so, yet made only one submission in the last month. A couple popular comments can heavily distort the averages.
Sorry about the confusion: by post I meant either news stories or comments, no distinction.
We could use the median rather than the mean, but I see no problem in the fact that a few very popular comments can pump up your average. They boost your absolute count too. And that's OK. Karma measures popularity.
I've picked up literally 100 karma in the last week or so, yet made only one submission in the last month. A couple popular comments can heavily distort the averages.