Face orientation should be almost always visible. Normals have impact on everything from tools and operators, trough modifiers to sharers and render. I like to help people over the internet and one of most common source of problems are flipped normals.
There could be an option to turn off visible difference not other way around.
IMO There are 3 major problem in regard of face normal visibility in current 2.80:
In solid mode frontface shading looks undistinguishable from backface.
I don’t know if this behavior is intended or not, but It will for sure will cause problems.
Face Orientation overlay looks like it is mean for only checking model at some point and not to work with it enabled. Color values and high opacity of 0.7 are hardcoded in glsl shader and cannot be changed.
IMO it should be configurable/themable or at least set to values that allow working with that constantly on.
EEVEE (and because of that also Lookdev) have only backface culling per material and there is no global setting for that, so if i want to work in Lookdev/eevee with backface off (cause sometimes they interrupt workflow) i have to write script that run through all materials and turn that checkbox.
IMO there should be also global option for backface culling in lookdev shading popover as before.
BTW is it still a case that backface culling speedup viewport?