Before leaving the subject of Polygon sub-object selection mode, we should consider the issue of normals. A normal (for our purposes) is a ray that is perpendicular to the plane of the polygon. This ray is used to indicate the renderable side of the polygon. The concept of a perpendicular ray only makes sense for polygons that are perfectly planar. Triangles are, inherently, perfectly planar. Thus in Editable Mesh, it makes sense to be able to display the normals for the Faces in selected Polygons.