You're working from a different definition of "good comment" than Graham is. The concern with "bad" comments isn't simply that they exist, but that they have deceptively positive scores.
...which is a problem with a crystal clear cause: if you allow purely democratic voting, then you'll end up with really popular crap reaching the top of the pile fairly often. Imagine how useless Pagerank would be as an algorithm if it considered links from every drooler with a domain name to count for the same amount as those coming from the frontpage of Yahoo - that's essentially what you're doing when you tally up votes on a site The only reason it's not worse than it currently is is that there's no real incentive for people to game the system, so we don't end up with massive comment spammers. But we still have douchebags, fools, and all other sorts of sheeple, and in large enough numbers they end up diluting the votes that should count the most.
Several solutions are probably obvious to everyone here and I won't go into them, but the point is, you'd have to be willing to throw fairness aside in order to fix the problem - if a brand new account's vote is worth the same amount as mine, which is worth the same as tptacek's, then something is wrong.