I'm not complete sure either, but I was able to remove the ear clip but not the jacket, but the next fight the boar were still able to zap his mind and the ear clips were still on his ears in the sprite animation, but I double checked after the battle, and he was not wearing them, it was not equipped in the menu
I know that is a different character in the script, so my best guess is somehow the characters got swapped in the wrong order, unless there's 3 or more versions of mezz in the script, if that's the case, whatever flag or variable that let the mind control happens is incorrect set to a different version