It's actually better to use white on black for computers since the light will "bleed out" light-to-dark instead of "bleed in", however most people are used to the black-on-white of normal paper and writing since ink, unlike light, has different properties and bleeds out dark-to-light and other such things I CBA to get into and damn this is going to turn run-on if I keep talking.
Because of this thread I've considered making a simple inverted skin for the forum, but there's some issues.
1 - It'd be a simple design, I prefer clean lines and such. Some people like flashy stuff as it signifies being new instead.
2 - Idunno' if the admins would accept and add it.
3 - I've never made a forum skin before so while I'm learning which graphics are used for what and where for this forum system somebody else that knows might make another one in the meantime and it might not fit the goals of mine so I'd be disappointed.
4 - The problem of text colors. While switching the default text color to off-white to make it show up on a dark background is simple, that brings problems for user-set colors. If there's a way to make all colors show their inverse that would seem to solve it, but then there's hue issues (the eye picks up more shades of green than any other color, for example) and the fact that people would have to make orange text for it to show up blue, since AFAIK setting a timestamp cutoff for the inversion is not anything a current forum system has implemented since a useful situation for it is so incredibly rare.