Seems I'm late to this thread, but can't resist commenting anyway.
I get the impression that some consider dim light to mess with darkvison. Since darkvison makes dim light act as bright light within the radius it obviously does not interfere.
Devil's sight had been stated to be intended as eerie since it would better without light at all than with dim light. I take that as:
1. Bright light is always bright light.
2. Dim light counts as bright light for those with applicable darkvison, gives disadvantage etc for others (lightly obscured?)
3. Darkness counts as dim light for those with darkvison, bright light for those with Devil's sight, heavily obscured otherwise.
So no reason to have light reduce our nullify darkvison, and the eerie part of Devil's sight is not upgrading dim light to bright light.