Regarding the mysterious glow from pawn to leaf:

It's an IDL bug - a new one. I investigated it some more.

IDL thinks the pawn is recorded as fully lit and bouncing lots of light, and in a strange rectangular pattern that doesn't match the pawns shape exactly. I performed the following changes to see if the artifact remains.

1. Change the leaf to black - gone
2. Change the pawn to black - gone
3. Change the leaf to not be a light emitter - remains
4. Change the pawn to not be a light emitter - gone
5. Turn off the infinite light - gone
6. Turn off irradiance cache - remains
7. Turn off IDL - gone
8. Turn off cast shadow for the leaf - artifact gone, but now there is real bounced light, in the correct pattern

The last test indicates it's not quite the same as if the shadow was turned off.

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Renderosity forum reply notifications are wonky. If I read a follow-up in a thread, but I don't myself reply, then notifications no longer happen AT ALL on that thread. So if I seem to be ignoring a question, that's why. (Updated September 23, 2019)