The problem is that polygons "technically" can't be double sided.  Either the normal is in, or its out, its not both. The double sided poly issue stems from making two identical polys, meaning both polys use the same vertexes, each with opposite normals.  This results in two polys in EXACTLY the same space.  Many applications just fry their brains trying to render two objects in the same exact space but facing opposite directions.  This typically results in the herringbone pattern as is exhibited by poser.  The application tries to figure out which of the polygons is closest to the camera.  The correct answer is NEITHER because they exist in the same position in virtual space but many applications' programming isn't set up to handle this condition.

What should happen is that when an app finds two polys that are exactly the same distance from the camera, it should default to rendering the one with normals more facing the camera, if that still results in a non-answer it should render the first one in the poly list and discard the 2nd one.