Dickens, Lloyd Alexander, and Terry Pratchett have spoiled me. They all take the time to make their comic relief likable. Now whenever I come across a grating `comic relief' I grit my teeth and wonder why the heroes don't find a way to get rid of the jerk -maybe put a sleeping potion in his venison and sneak away during the night.
Gail Carson Levine mentions here that one way to make your audience enjoy a character is to show that other characters like them. I love it when an author gives me some solid reasons why the heroes want to hang around with the comic relief. In Dicken's The Pickwick Papers, Sam Weller is sarcastic and far too mouthy to be a conventional servant, but he's also clever and fiercely loyal to his friends. At one point he deliberately get himself arrested so he can follow Mr. Pickwick into debtor's prison. You gotta love a guy like that.
The best comic characters have a wider emotional range than just cracking a joke -then cracking another one- repeat into infinity. Moist Von Lipwig from Terry Pratchett's Going Postal may not admit that he feels anything beyond enjoyment at outwitting the next mark, but with his slowly growing desire not to let his friends down, and the discovery that he has something to fight for, he becomes a very endearing -and well rounded- character.
I guess what I object to is people who don't treat their comic relief like real characters. But then, I've never appreciated slapstick humor, either. To me, pies in the face are just mean, and if they're always thrown at the same person, that's bullying.
Maybe I should start a Comic Relief Union?