I don’t think it always happens, I think it occurs with a combination of things. Lighting and render settings play a part, as you foundwhen the render is la large size the lines disappear. the more complicated the shaders and lighting get the more things have to be tweaked depending on the image, at least thats what I’m finding.
I do agree there I just tried out the parameters from M5 Dave Elite… Which uses SSS… I simply replaced the SSS Mats with Interjections, added my own character Diff with Bump and Spec (I havent changed the M5 elite settings such as colour and stength yet) But A quick render revealed under the same Lights and render settings, I HAVE NO lines LOL! Very weired. Perhaps the skin parameters I used with two layers of spec, Both dif and SSS mats mixed with to make up the settings for SSS had played a part in the issue.
Dunno… But here is the test render using M5 Elite parameters with Interjection SSS Mats.
FYI - the SSS Scale IS 1.70
Click thumbnail to see full-size image