The key word here is “personally”. Personally, I can't read anything with dark background at all. It only takes a few seconds before everything starts swirling in front of my eyes, and when looking away from the screen everything around me starts to look weird. It takes several seconds for me to return to normal.

I've been told this can be caused by astigmatism (which I have), but I haven't spent much time researching it. When I come across a web site with dark background (thankfully quite rare) I use a Chrome plugin that can fix it, and it works reasonably well in most cases.