There are two problems with what you say. First, a large number of posts with a small number of upvotes is still valued more by HN than a small number of well-respected comments. Second, moderation systems tend to be inflationary, which means that the point value of a given comment has more to do with how many people read the thread than anything else.

Slashdot's point cap is the obvious solution, but even there comments tend to lean heavily towards +5 on well read threads.