[Fortunately he doesn't follow up with another attack after that, but it's largely because he tries to wield Muramasa as little as possible and that seems even more important around Riku! The blade's still out though, just in case this is all a DISTRACTION and Riku is just waiting to kick his ass as soon as he gets distracted by samurai talk.

Please understand that even though swords aren't keyblades, samurai ideals basically make them as such.]

No - samurai come from lineages of warriors. Not everyone can wield a blade. Many families - especially larger or more established ones - do pass along their swords, though. My-- real sword, Hotarumaru, is an heirloom. [THAT HE THREW AWAAAAAAY his guilt...] A wavering heart will affect one's ability to attack or defend, as well, so I would say that's true.