User blog comment:AYET/Luffy loses an arm/@comment-137.150.161.170-20141002000418

Eh... I don't think he needs the added 'handicap' to increase how legendary he'll be. Kind of goes without saying when you become the second Pirate King, y'know?

Not to mention what everyone else has already said about how Haki works, but hte key thing is that it doesn't matter how he has some kind of pseudo-limb because he's probably not going to loose it. And if he actually drags Law along full-time, then if Oda actually goes that route Law can slap on a far-more-interesting animal-limb.

Besides, it's actually what Luffy would want. Heck, it's probably the most he'll get out of Traffy, considering he'd start asking for a bunch of other random stuff (including Kin'emon's legs to be a Centaur agian) and Law will have to cut him off at the pass.