hate to beat a dead horse but:
considering the danger of the battle, and the fact he probably occupied zoro's analogous niche within the whitebeard crew … why wouldn't marco the phoenix cut his arm off after getting shackled with kairoseki cuffs? watching the anime now, that just seems off. as first division commander, he'd probably have a similar tuffness and seriousness about him, and we've seen zoro make the pragmatic (and desperate) decision to cut through THREE limbs to save his crewmates so far: legs in litte garden, right arm in enies lobby.
and to make it more obvious, marco would just be able to regenerate the arm after the cuffs fell off. this just seems wasteful. i know why oda did it, and i'm pretty sure he has plans for marco in the new world, so he didn't want us to see the phoenix fight at full strength. but .... damn ....