Gravity exerts almost no torque here. Philae has 100 kg of inertia, but it weighs less than a feather. Even if were in a strong gravity field, that still would

Gravity exerts almost no torque here. Philae has 100 kg of inertia, but it weighs less than a feather. Even if were in a strong gravity field, that still wouldn't orient it, if there's no force like air resistance to attenuate its tumbling. It can rotate indefinitely in the vertical plane: there's no loss of energy. (In an atmosphere, this rotation is damped by air drag, so gravity can orient things).