Phoenix down seems to have no effect.
This is just a wild guess, but I have a theory. If a character is killed, you let their HP go negative, yes? so maybe Merovingian has 76 HP left, and he gets attacked and killed with 140 damage. That should leave him dead with -64 HP, right?
Then Mai uses a phoenix down on him, which is supposed to revive him with 1 hp, but instead it just adds 1 hp to his current value, leaving him still dead with -63 hp. Could that be what is happening?
EDIT: Also, some dances don't seem to do antyhing. Slow Dance, Wiznabius and Last Dance seem to have no effect. Polka Polka seems to work just fine.
EDIT: Also, it appears that when you have two weapons attacked, damage is not displayed properly, even though damage is inflicted correctly.
80: Marius (A) attacks E10. It misses Mai (E). Mai (E) Mai (E) dies!