Dave Winer says that MoveableType's RSS support is "funky". Aaron Swartz offers an extensive and sensible survey of the question.
I still don't understand the issue, or why it matters. I'm running a major development effort that supports RSS. I don't care about personalities; I just want our RSS to work with everyone else, and everyone else's RSS to work with ours. Come on, folks: can we please talk about the tech?