This is just a new algortihm for general sharpness, not especially the galaxies. I asked Vladimir if he could keep the old one available because the new one can has unwanted effects on some config/resolution.
Galaxies/nebulae have theor own sharpness pass, but it was disabled, because the global (scene) sharpness did the job even better. And having double sharpness makes them over-sharpen. Now I added adaptive sharpness pass for galaxies/nebulae, which is reversed to the global sharpness slider value. You can disable this "auto sharp" in the debug window, if you with to have oversharpen nebulae (SE will remember your choise in the config).
Screenshots for comparison - open in the new tab.
All sharpness is off.
Galaxy/nebula sharpness is at 1 ("Volum sharp"), global at 0 ("Global sharp"). Stars are not sharpen, looks the same as in previous screenshot. Nebulae are great now.
Galaxy/nebula sharpness is at 0 ("Volum sharp"), global at 1 ("Global sharp"). Stars are sharpen, which is acually unwanted. Big nebula looks almost the same. But look at the pink sprite nebula near the left edge, and at the tiny nebula near the bottom. They look much better now! Global (CAS) sharpness works better than a special nebula sharpness pass.
Both sharpness is at 1. This is too much IMHO. Note oversharpen black blobs in the big nebula.
So the "Volum auto sharp" checkbox enables adaptation, so that "Volum sharp" is locked and its value = 1 - Global sharp value. The same system is used for 3D rings ("Solid sharp"), because they look especially horrible then sharpness applied twice.