Although I agree that flipping seems to be more of a swashbuckler thing, consider how heavy the weapons buccaneers use. Considering that most characters can't even LIFT almost half of them without some training, how do you expect them to do a backflip while swinging one of them? I'd say that if they can effectively use swords in combat that are almost as tall as them, why can't they do a flip or two while they're at it?