Hi, Andy, this looks great. Don't know about the lighting glow in the shadows, maybe you have high exposure or GI strengths that are affecting it.
I do notice, however, there are a few nasty holes in the terrain where the displacements have 'torn' the planet geometry a bit, they look like 'hot pixels', white holes where they shouldn't be. Sometimes, increasing 'displacement tolerance' in the planet node can help this to some degree but, it won't always remove them completely. Small areas of the terrain are being stretched to a large extent by the displacement of the terrain shaders, try isolating one fractal at a time and edit its scales/displacement amplitude one by one to try and track down the culprit shader. It usually happens when a shader stretches part of the surface to a completely vertical edge, when there is a very little portion of planet surface being stretched by excessive displacement.
It may also be from the strata shader's settings 'hard-layer steepness'.
Nice shot and any of those discrepancies aren't your fault, just TG idiosyncrasies, you just need to work around them.
