Hi Michael, it sounds like you've got it all figured out, that it's just a display issue that you can configure in Rhino. Basically Rhino was originally designed to work with a wireframe display and when you're only drawing wires and no shading at all you need some way to try and see surface shapes and that's why it shows isocurves like that by default. They are just basically curves drawn at some regular intervals along the U and V directions of the surfaces.

There are some various remnants of that original wireframe display orientation still in Rhino, some of which are pretty annoying like the wireframe of selected solid objects showing up on top of everything.

MoI was designed from the ground up to use a shaded display instead.

- Michael