You don't say how you are using the platform behavior, so I'm assuming you're using just the default keyboard commands. What you need to do is override those defaults -- do not turn them off, but just insert a keyboard object into your game and then add an event to redefine the left and right keys to make the player move in the same direction as the key, but also add an action to mirror or not mirror the player to make him look the way you want him to.
I think redefining the keys and mirroring the player is described in the two platformer tutorials. They're pretty popular, so you should find them on the first or second page of the tutorials. I'll have a little more time tomorrow, so if you don't still don't get it, let me know.