I have a theory.

Skin is very hard to tone map. No that isn't the theory. That is an observation. I pretty much always get a great deal of noise in skin. I have this probably idiotic theory that it has something to do with the mottled nature of skin or sub surface scattering or some such.

If you have ever watched a really talented artist texture skin on a movie model, you realize that the visual effect of skin is much more complex than it seems. Skin almost glistens and it has several layers of texture that you can actually see. Somehow it really seems to bug tone mapping.

Or am I just imagining it?

I have not tried it

but I'm sure it will make any imperfection pop and become very visible besides giving it odd colors

the same way it exacerbates the texture on stones and bring out otherwise invisible tones.