This is my mesh before subdividing:
After subdividing x3:
After un-subdividing x3:
The diamond topology mess up smooth shading and make the edges look terrible from certain angles.
It might seem like there's no point in subdividing only to un-subdivide, but the purpose is to get the smoothness that subdivisions give, but still retain a low poly count. How do I obtain to a low poly count, but keep the smoothness of subsurf and decent toplogy?