In fact, I have posted in the past some glitches regarding viewport realtime rendering with an AMD Radeon Pro card. I have been asked to post the second glitch it in a different post so here it is.
It seems that the clipping plane does not clip the outlines of the objects unless they are fully clipped.
However, I have recently downloaded the latest versions of Rhino 6.0 (6.25.20105.13371) and Rhino WIP 7.0 (7.0.20105.12495) and I was surprised to see that for Rhino 7.0 doesn’t appear to have this issue anymore.
Some screenshots below:
Rhino 6 - Shaded
Rhino 6 - Wireframe
Rhino 7 - Shaded
Maybe you could correct this bug in Rhino 6.0 as well?