>>8664120
>>8664098
Okay, so it turned out "shaded face" is a tag on Danbooru with 64K hits. Even if it's not in prompts it could have an impact on gens in general. There's also "shade" which is supposed to be the correct tag with another 17K hits. And tagging is imperfect so there could be even more that aren't tagged.

I think >>8664098 had the right idea that in this case negative tags work better than positive tags. Pic related is a test with negative tags. It seems like "shade" or "backlighting" in the negatives works the best.

Thanks a lot for bringing this up! It's the kind of thing I may have never noticed otherwise but it does make a significant difference in the look of a gen. It's a really good thing to have in mind for future gens!