What happens to light when it hits a feather, does it get absorbed by the feather, does it leak out of the diamond, does it reflect back and is it the same with crystal inclusions in a diamond? Is it too minute to tell unless under 100 or 1000 times magnification!
All of the above and maybe none of the above: ie it passes through the feather and hits a reflector and is reflected out just slightly disturbed.
All depending on the exact inclusion and placement and how the light strikes it and the strength of the light.
Crystals are usually dense enough they absorb the light I would guess. In theory they could pass it or even reflect it I suppose but wonder how likely that would be.
It would be fun to hit a diamond with a laser and see if it could be seen in a photo what is happening when the light hits an inclusion.
Not very safe however.....