I don't know. I mean, Batman intentionally ripping someone's mouth open? That seems too sadistic for Batman.
Now, I could see him being in the middle of a fight and forearm a guy, which would lead his gauntlets to gash his face, but I can't see Batman cutting someone's mouth for the express purpose of cutting their mouth.
There's a big difference between that and the stuff Miller had Bat's do in DKR. Yeah, Batman broke bones and all that, but in each situation it was to incapacitate the villain. Cutting someone's mouth doesn't put them out of action like breaking their leg would, it only puts them in lots of pain, but they would still be very able to fight.