The visual effect of fog, and particularly ground fog should be fully controllable by the creator. There are many conditions on earth where visibility for 5 to 10 miles is possible and fully understood by the viewer, but Sansar does not make it possible due to the current implementation of fog.
Flying in a plane at 50,000ft (about 10 miles high) it is often possible to look down at the earth below and clearly see features on the ground. This would not be possible in Sansar because of fog.
With the current implementation of fog, there is no practical way to simulate outer space. Outer space simply has no fog. And the transition between the "sky" and the ground actually has no horizon. Outer Space in that context is omnipresent and uniform.
Below water, diffusion and dispersion would darken rather than lighten the scene as the distance got further away from the viewer. The deeper one goes, the darker it gets. And obviously there is no such thing as fog in a water environment.
As it is currently implemented, the visual effect of fog is just too confusing and it is creatively limiting.