Apologies if this is the wrong place for this, but if what I mention can be fixed, it might be?
This may read strange, but Atton has a vertical line going down his forehead, but not his entire face. I don't think this is the black line issue that is fixed by GLOverride, as it does not fix it here and does not run down his face. Futhermore, Atton seems to be the only character in TSL with this problem, no other NPC has a line in their face. The line does disappear if you turn off MSAA and put anisotropic filtering no higher than 4x, so there might be a connection there.
The head texture is (probably) not the issue, as retextures do not eliminate it. Which leads me to think there's something up with his head model that causes the problem, perhaps only on certain hardware or graphics settings. I did try poking at it with KOTORmax, but didn't get very far.
Could something in his head model be changed to fix the problem? If not the head model, maybe the UV map?