My question is this: so you're saying he was completely enveloped in Mugetsu, but for some reason only his wings were being destroyed? How does that work? The entirety of his body looks different after he gets hit by it. No holes in the middle of his chest, no wings, no monstrous faceguard, etc. Combine that with Mugetsu clearly eclipsing (heh, moon pun) him in terms of size when he gets hit in chapter 421, I'd think it makes more sense that he just.. got completely hit by the attack. Doesn't make a lot of sense for Ichigo to think only cutting him in half would do the job, is all I'm saying.