I havent ever painted a skin texture for 3D figures, however I have done 2d portraits a lot.  Now in painting 2D faces and bodies it IS the highligths and shadows  which bring out the form and depth of the face [or whatever].

What I think I'm reading  is that  in order for texture artists to avoid 'baked in attrocities' they should totally omit this shaping and forming with shadows and light; rely solely on the underlying mesh with lighting to provide those,  and  just paint a plain even flesh tone with only tinting/color differences and  possible blemishes at various areas.  Am I right in this assumption?  Is this  an accurate description of what's needed for good textures for 3D figures?

What about with photoes used for texturing?  what exactly is needed there?   Doesnt even the most evenly lit photo create hilites and at least some shadows?

I'd love to hear exact artistic definitions  for good texturing of 3D characters.
Thanks :)