I'm not sure what I'm not understanding...
I'm a "polygon modeler", so I'm not used to all the difficulties with Fillets and Chamfers, and the "broken edges" that I experience when learning modeling in MoI. There must be something fundamental that I'm missing because I really struggle so often when trying to add Chamfers or Fillets to my objects.

In the attached examples (3DM file included), I start with the thin joined surfaces. They look clean to me… I offset this using the "Shell" command, and now this is a "solid". When I select the highlighted edges, I can perform a partial Fillet on the edge (but it's limited to only half the thickness of the shell). And the Chamfer doesn't work at all?

What is it that I'm missing? Also, is there some kind of "optimize" command that cleans my model from corrupt edges and welds edges within a certain distance?