On Linux, the effects of light on regolith layer on top of the map are visible on the bottom of the map, in magma layer. I haven't seen it happen on Windows, but it does happen on Linux.
Pretty sure that's a OpenGL vs Direct3D thing: they have Y coords for framebuffers going in the opposite directions, which affects deferred rendering if not taken into account.
On the screenshot, all the light "rays" go from the bottom to top - there are no "islands". This supports my interpretation.
On Linux, during the day, look at the bottom layer of the map.