Stout
Hold onto the ball, Murray!
I just caught this line of your post now (sorry).
My original point was that I don't think the joker should be played "funny." I think he ought to be an f'd up psycho killer that always has a smile on his face and laughs a lot at inappropriate times, maybe makes a wry joke here and there, but mostly his look of a clown is juxtaposed against his startlingly frightening demeanor.
The joker doesn't have to ACT like a clown, he just has to look like one.
Hell, how scary would he be if he didn't speak at all--just laughed, but was otherwise silent?
I think there are a lot of ways to play that character, and if the director is looking for a comedic actor, he's already increasing his odds of failure because, as you noted before, he'll be compared against Romero and Nicholson. If Ledger plays it different, he won't be to the same degree.
I agree that it would be a creepy and fun direction to go, and I think that is the direction they are taking. Again, though, is Ledger that kind of actor either? Not really, from what he's done so far. He's more of the young ingenue or leading man. I will remain skeptical.