When it comes to Dark and Light characters, since they can never really be at a complete disadvantage, Element Penalty buffs on moves are useless to them. Though you could switch out a move, it is confusing to have a single buff that only specific types can use as if the buff was designed like a catalyst. So, to make it fair to all types, I suggest that an alternate effect be added to the Element Penalty buff that's specifically designed for Dark and Light characters, and therefore unusable by the Triangle Elements.