And here is with 1 bounce. The underside of the large square is catching some light, revealing some stuff that wasn't visible at all in the zero bounce pic.  All of the light illuminating the revealed stuff is bounced light, there is no direct lighting being cast on it.  Big ugly artifacts (low quality settings, 25%).  The smaller square is completely black (it's only 2/2/2 because of Tone Mapping, which I realize now I should have disabled for this test).

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