Shock Ability

It's not a bug in terms of the original game. It's precisely intended to work that way, as blanking out MP is a way to hide the fact that any of your main characters could learn magic under the right circumstances.

I'm aware of that... I said it was "kind of a bug", because it is odd behavior for a character with no magic command to be able to learn a spell they can't use, but they obviously didn't plan on any main character not being able to have the magic command. I've been playing FF3 SNES since the day it came out, so I'm not some noob about the mechanics of the game; I simply haven't done any hex editing before.

In addition, temporary guest party members like Leo are unable to learn magic due to their actor ID being beyond the bounds for learnable characters. If you didn't change his ID in your hack so you could enforce his "no magic" status, that would also cause a problem with MP-battle related things.

My hack is based on fedorajoe's General Leo edition, and he used the Shadow slot for Leo.