[rujuladanh]

I almost agree with you, but the truth is even with almost minimum brightness, I still prefer that background color get slightly darker than pure white (and same in black backgrounds: the text should not be perfect white).

[close04]

Sort of like the way HN implements it. Grey or something off white tends to be easier on the eyes than pure white.

Reflective media like paper behave a little differently than emissive media like an LCD. A normal sheet of paper under normal lighting conditions won't reach the same brightness as an LCD. An LCD is much bigger than any reasonable book and it emits light uniformly across it's entire area (close to impossible for any piece of paper unless it's affixed on a flat plate). Also most paper is not actually very white.