> But an e-ink display on its own at least removes an additional light source pointing directly at the eyes, which could provide a potential mechanism for different effects on the eyes/brain.

Not really, since LCD/OLED aren't an additional light source, but absorb and thus replace the ambient light that would be coming from their direction.

I don't know the science, but my experience is that my brain is simply able to process and retain information so much better with eInk than with LCD screens.

I started as a teenager with cathodic tubes, which were killing my eyes and bringing daily headaches; moved on to LCDs which stopped the headaches but still tire my eyes significantly (some of them literally make me cry after a few minutes); and then found eInk and it's so much better, I will definitely move to that once prices of large color monitors at 60hz get into my price range. I honestly don't care about power draw one bit.

Not really, since it's not just about the light intensity, but also its spectral power distribution. This especially matters when using the display in a darker environment with low-temperature illumination, e.g. when reading before bed.

Quick experiment to show the effect: Go into a room with low 2700K or lower-temp lighting. Take an LCD, set its colour temperature same as the external lighting, then display an all-black screen. Since the screen is displaying #000, the software colour temp adjustment can't do anything, and you'll see the screen as emitting blue light, the colour of its backlight.

OLEDs don't have this issue, which makes them great for night-time use when configured properly, but they also generally use low-frequency PWM dimming on low brightness.

> Not really, since LCD/OLED aren't an additional light source, but absorb and thus replace the ambient light that would be coming from their direction.

Don’t they actually have to over power the reflection you would see with the screen off?