We're talking about Cryostasis here, right? See what effect the in-game settings have on your config.cfg. The "Texture resolution" setting in-game and the "r.diffusemap" in the config.cfg are one and the same (with 0 being High, 1 Medium, and 2 Low).

Wow, you are right. This makes absolutely no sense. Diffuse mapping/lighting is not at all related to texture detail.

That is wierd. Thanks for explaining that for me