Yeah, it's an animation method to allow for them to animate the mouths w/o having to deal with the teeth too. Your toon doesn't just keep it's mouth closed.
yeah they do. As a 3D modeler myself, I have to give a tip of the hat. The people who developed the art for this game have mad chops.
It would be nice if our characters talked once and a while, the occasional WOOOOO if you're in the air flying, jumping from a high place, or gliding,( It varies for each and every personality, morality, and character) you have the option to shut them up but still, it would be nice to see those eugh, "teeth" be used once and a while for actual purposes instead of our characters silent screaming.