Hm, I think I wasn't clear. I'm interested in comment upvotes per comment, not top-level post upvotes per comment. My assumption is that everyone here is primed to upvote due to the content of the post that most of the comments here are highly upvoted.

Or maybe you really did measure that that? You are probably right that some long-lasting classic posts have gotten high numbers of upvotes on their comments over the years just since so many people have read them.