Here is how they behave with all scene lights turned off.

Without lights, all diffuse effects generate black.

But since my sky sphere is self-lit (glowing, emitting its own colors from a photo), then the reflection still works.

This is what gets screwed up if you have those checkboxes turned on.

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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)