this is the worst kind of pedantic engineer comment that seems to infest this site. they're obviously talking about the frontlight. dark mode reflects much much less light back at the user through the lightguide because the dark bg absorbs more of the light.
It wasn't obvious. My thought process was that they were equating ereaders with eink displays, and they had a non-eink ereader. To me, emitting light and reflecting light are completely different.
(I suppose I'm not supposed to feel complimented by the term 'engineer'? I'm not trained/experienced in any engineering discipline, not even software engineering.)
If you want pedantic ridiculousness, well, notice that I never said that the e-ink emits light. It does, however reflect light back from the device's frontlight. The device taken as a system most certainly emits light, but less so when in dark mode.