Linus has been here two years and he's not a Knight. Of course, I think he would probably impale me with a harpoon if I asked him to be one, but that's a whole different story.
And yeah, Knighthood is definitely on a "don't call us, we'll call you" basis. The decision's made by the entire staff (So there's no one person you can kiss up to, and over half of the staff will dislike you for kissing up to them anyways), usually based on a member's personality; You can train a monkey to open or close threads, it's the person who makes a good or bad moderator.
I can also confirm what The Man said. He missed out becoming a Knight by one vote, but someone leaked that to him and he's been trying to run the board for us ever since, so now I don't think he'd get a single vote if someone nominated him for Knight