When I use clouds for like fog, and stick a SSS model in it, it seems to glow with the cloud colour, despite volume density and colour at one and even ramping down decay distance to nearly nothing. So when I mix together the SSS and default shader, the transmission areas are glowing. This explains why I couldn't use SSS on my Derelict scene because of the godrays haze. I thought it was just scale and I couldn't find a sweet spot for SSS and gave but, but even here, reducing to nothing doesn't help.
First screen: SSS only
Second screen: SSS Only
Third screen: Default shader only