Isn't "karma / #stories" a bogus measurement, considering that karma is obtained both from stories and from comments? I (as I write this) have 89 karma, but only 8 points of that is from submissions...
How about computing [karma obtained from submissions] / [# of submissions] and [karma obtained from comments] / [# of comments] separately?
How about computing [karma obtained from submissions] / [# of submissions] and [karma obtained from comments] / [# of comments] separately?