Apparently light-on-dark is terrible if the person has astigmatism: the edges get very blurry and doubled. There was an article on HN about this, specifically about keynote slides. Also apparently “in Europe and Asia, astigmatism affects between 30 and 60% of adults” (says Wikipedia). I have it too, and couldn't figure out in the past why text sometimes looks horribly blurry and sometimes doesn't. With this knowledge…
That's true for me as well. I couldn't read the oven clock (blue on black) at just 10 feet away. Anything bright on a dark background is just a blurry radiation pattern. The reason dark-themed terminal and coding is fine, might be the monospace fonts. They are square-ish, so there is less need to find the edges accurately. They are also eligible on very cheap, trashy screens. As a side effect, code is readable in dar…
I have good vision: no known issues, regular eye checkups, etc. But I find it nearly impossible to read most displays that use blue LEDs. If the background is blue (eg: timex indiglo watch) then it's fine. But blue leds on some of my home theater equipment drive me insane. Even if it isn't the letters/numbers themselves and it's just a regular circular power led, I find them really hard to look at.