Deadpool grew his head back. No reason to believe Wolverine couldn't do the same, it'd just take longer.
Wolverine gave the sword to Cyclops, explaining it by saying: "This is the only thing in the
world that can put me down for good."
The mystical properties of the blade mixed with the fact of decapitation means game over friend.
"Muramasa Blade doesn't cut, but slice the matter at molecular level. Wolverine's regeneration power is meant to work from cell or any biological level. As blade cuts on molecular level, the organic matter is destroyed (organic matter is made up of many molecules). So, his regeneration fails to work."
It's not explained fully but that fact that both muramasa blade's can kill him is canon...us arguing over it won't change fact.