Design decisions are simply tools to accomplish these goals. Jeff says disallowing downvotes is "harmful to the community" and explains why he theorizes is the case, but why guess? We have HN, we can examine it and decide for ourselves if HN has been "harmed."
I am all for him beating his chest and extolling the virtues of his complicated system. But I do not see the merit of his comparison to HN: It strikes me as fairly run-of-the-mill Coding Horror-style link-baiting.