Hi Steve - yes that's correct, typically you won't edit the polygon results that you export from MoI, once you export the model you can use it for rendering or uv mapping or stuff like that, but it's not particularly suitable for tweaking.

Re: All quads - the mesh generated from MoI is more oriented towards a light polygon count that is structured like the original NURBS topology which is a pretty different thing than generating all quads, see here for some previous discussion on that:
http://moi3d.com/forum/index.php?webtag=MOI&msg=4600.1
http://moi3d.com/forum/index.php?webtag=MOI&msg=3628.227

If you try to do stuff like bevel the exported mesh, you'll also mess up the stored vertex normals, C4D will have to calculate completely new vertex normals from the polygon data and that will tend to reduce the quality of the shading by quite a bit since automatically generated vertex normals don't really work that well on mechanical models where you've got things like large polygons next to small ones, auto normal generation tends to work better on organic models where you've got all more regularly sized polygons.

The vertex normals that MoI writes to the OBJ file come from the original NURBS surface so when they are used it helps to ensure that the polygons are shaded to look the same as the NURBS model, regardless of what kind of topology they happen to have. So you really don't want for those normals to get discarded, you get the highest quality shading and reflections when those original normals are used in the rendering. So that's another reason why you generally don't want to edit the mesh in some way that will cause vertex normals to have to be recalculated in C4D.

If you did want to edit the polygon results out of MoI, you would probably be looking at some process like using a retopologizing tool to lay quads down over the MoI-generated mesh to restructure it. There is a program called Topogun which is good for this, and also 3D-coat has a set of retopology tools for doing that kind of work as well. This is usually quite a bit of work though, so it's not really the main way of using MoI's output, it's more typical to just render the result from MoI.

- Michael