Actually what Dan did is sound. Decreasing gamma correction would also darken shadows - as we know  that's the point, right? So doing so near the terminator makes sense and does the same as decreasing the effective luminance of the Diffuse node as I suggested. The curves come out slightly different, but we're talking subjective stuff here so there's no physics to be tracked. And also using the Tint does similar stuff - reducing the effective diffuse reflectivity, but independent control of each RGB channel. Doing both - not strictly logical, but it gets you there.

I didn't realize you wanted to also redden the terminator - my setup was only going to soften it. However, if you wanted to take advantage of the built-in relationship between diffuse reflectivity and sss reflectivity, you could get a softer and redder terminator with only two nodes. Unhook that Blender, and just connect the Math:SmoothStep to PM:Diffuse Reflectivity. Observe the change in the preview.

Here's the logic - a photon approaches a skin. It strikes the air-skin boundary - does it reflect (specularly) here? A percentage will (controlled by Shine parameters). Those that don't, they enter the skin. So a photon has avoided specular reflection and now it is in the skin/pigment layer. Does it enter a molecule and then reflect (diffusely) here? A percent will (controlled by PM:Diffuse Reflectivity). Those that don't, they enter the deep tissue, and experience sub-surface scattering. Of those, a certain percentage will come back out (PM:SSS).

So the moral is:

More shine = less diffuse + sss
Less shine = more diffuse + sss
More diffuse = less sss
Less diffuse = more sss

Nobody in Poser land has modeled a skin shader this way before, as far as I know.

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Renderosity forum reply notifications are wonky. If I read a follow-up in a thread, but I don't myself reply, then notifications no longer happen AT ALL on that thread. So if I seem to be ignoring a question, that's why. (Updated September 23, 2019)