One reason I suspect Daring Fireball posts get upvoted so much on Hacker News: You can comment on them here; not so on his site.
Hardly a new account, though it is his first comment.
I don't think it's him, though; I imagine the real Gruber would have tried to take http://news.ycombinator.com/user?id=gruber (which is still available), so as to match his Twitter username.