Upvoted comments are directly related to the user's comments, and thus the user, so that makes sense. Articles are not related to the user* posting them. It's basically random unless I'm missing something.

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.