In many workflows (rendering, 3d printing) coplanar or overlapping faces cause issues down the road. With complex models I have no hope for automated fix of this condition, but being able to see where the problem occurs would be already very helpful to fix it early.
I wish there was a Analyze tool or a DisplayMode that would highlight the mesh faces (using render-mesh for non-mesh objects as well) that are overlapping - one shade for any face that overlaps and another shade for the area of overlap. Then a button so select such faces.
I have seen it in other few other programs but having that inside of Rhino where 90% of my modeling happens would be extremely helpful.