Gah - a solution with more questions. – EntropicLqd
Legacy:Unlit Surfaces
From Unreal Wiki, The Unreal Engine Documentation Site
Unlit surfaces are surfaces that have no lighting or shadow detail.
This does not mean that these surfaces are not affected by light, but that they are not affected by lights or shadows.
I was unsure about this when I started mapping. Hopefully this will clear up any confusion, if any exists.
This is a picture of an unlit surface:
