I think HypCo's suggestion is fair, as far as giving warnings.
If I were playing Ygne differently, and she'd be the one to kill a PC, then she'd likely do it in an instant where there are no possible warnings to give (while they're sleeping, for instance). But, while Ygne may not mind, depending on the circumstances, MoMo probably couldn't live with killing another player's character, because I'd feel bad. That said, I'm aware of the kind of character I'm playing, and if Ygne mouths off to the wrong PC and she gets herself killed for it, that's totally understandable to me, and I'd be okay with that (because likely any warnings given wouldn't deter her).
I think it can also be fairly neat if a fight between characters doesn't require rolling and rules, and could be resolved by player discussion/agreement and then narrated, maybe, but I don't know how everyone else would feel about this.