Load this
CP_EdgeSoft.3dm (63.2 KB)
in V8, and apply an edge softening 0.1.
See this:
Rhino was too nice and shows the defect in an arrow shape, pointing to itself 
It doesn’t matter which softening size or which rendermesh settings, I always see the defect.
In V5 with the same file, all is good.
This issue is old and came up in V6.
To draw attention to V8, it is now here in Serengeti.
This could be related to the kink between the two adjacent surfaces.
I duplicated the surfaces with edge softening on and scaled them with factor 0 which results in a planar object.
Interestingly deleting the selected surface in the next screenshot and capping results in correct edge softening.
Didn’t try that before.
While the kink is still 1.17°, the softening is ok.
I tried different render mesh settings in the original file.
But always get the visual defect.
It would be good to know how to handle this issue.
Which setting is meant?
This is active in your file, same as in my file:
