I’d like to report what I think is bug, introduced, I believe, in 5.7 but prevailing in 5.8. Below is a picture from an OpenFOAM case, with “surface with edges” visualization turned on.
We are looking at the corner of the box forming the simulation domain, and what we see is that the grid from invisible surfaces leaks through!
UPD: A slighly better clarification. The side facing us only contains rectangular cells. The bottom surface, which should not be visible at all, is meshed with triangles, and these are leaking through. The surface alinged iwth yOz is meshed with rectangles and these are also leaking through a bit.