If one takes a four verticie polygon lying flat on an x - y plane and move one verticie in the z direction, it is no longer a real face. If you look at it one way, it appears to be a four pointed polygon, but at another it appears as if it were made of two triangles.
How do you treat this kind of mesh form when you are modeling?
Is it good practice to eliminate them, or does it not matter and you disregard them? What are the cons and are there any pros to this kind of paradoxical form? In what situations are they clearly undesirable and what situations is it too much trouble to correct them?