Upvoted comments do get karma, just as upvoted stories do.
Like I said, I upvote all submitters of the same article because otherwise it seems wrong given how karma works now. But we shouldn't have to do that.
Edit : * With the exception of Ask HN or Show HN, I suppose. But the vast majority of links are from external sites and submitted several times by different users.
I agree that there's an issue with randomness about which submission of an article gets the karma. It's on our list to do something about that. But it does even out in the long run for anyone who submits many good stories. And I don't think most HN users care about karma too much.