[mrob]

What objectively measurable difference is there between reflected and transmitted light?

Polarization might be different, but that's something that's only barely perceptible to humans. I don't think it's plausible that it could affect legibility or eye strain. ( https://en.wikipedia.org/wiki/Haidinger%27s_brush )

[s_kilk]

Energy transfer.

There's a big difference between absorbing reflected ambient light and having photons pumped into your retina.

[aetherson]

What? No. You obviously receive way more energy via sunlight reflected off the page of a book than you do via your LCD screen. That's WHY you can't read your LCD screens in direct sunlight.