It can, but mostly it effectively decreases contrast. Blurring decreases contrast too, so it's hard to tell sometimes what the dominant effect is, and in small amounts you can get away with doing either.

Suppose you accurately model a diffuse layer and sss layer. Your diffuse layer would not take up all the light - some is diffusely reflected immediately and some goes down to below the surface.  Then the subsurface calculation takes some of that light that passes through and spreads it around, or gives it back out the same point, regardless of the diffuse color at that point.

If you have a surface that is reflecting small stripes, alternating light and dark, then a partial diffuse reflection would darken all of it  then some of the light will leak out everywhere, brightening everything. The end result is a blend of the diffuse color and the sss color. So this effectively fades the diffuse texture.

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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)