I'm going to defend myself by saying that if it's okay for large development studios working with dozens or hundreds of people to do then it's okay for me too ;)
Also, I'm a solo dev and I'm not manually flipping every single asset - that would double the fileseize of the paperdoll assets and my workload. The "flipping causes a mirrored effect" is true for everything from eyepatches to shirt pockets so if I manually create a flipped version of Ami then I've got to do it for everyone.