I have a little information on this: Footprints are determined by the geometry of leg joints. That is, the direction of a footprint is determined by the joints of a particular creature’s legs and ankles. For all the races except Charr, those bones bend in the same direction of that of a human, they each have the same “ankle roll.” But if you look at images of the Charr, the ankle roll is different. And it’s the way the leg is configured that results in the footprints being backwards for the Charr. Or, as an artist said, “Once the Ankle goes over the ball of the foot, as it does with the Charr, the footprints get reversed because the (game) engine thinks the foot is pointing the opposite direction.”
In Guild Wars 2, the Charr are a primary playable race with significantly unique designs (i.e. they are giant bipedal cats). I never have personally noticed that Charr footprints are backwards, but for an entire playable race to be given such treatment, that’s very odd.