As far as RAT goes, I don't muck with it; to me, anyway, the CSS for that belongs to individual users, not themes. My account has left PerlMonks' defaults, and though it's a bit ugly, it isn't horrid, eye-popping, or unusuable. If you have a theme patch that makes it nice and pretty, I'd be happy to accept it, though.

As far as the replies go, I don't see that problem on any platform/browser combo. I override the bgcolor tags using CSS, so it shouldn't be an issue. Perhaps something in your user-custom CSS might have created the problem? Just guessing, here: I simply can't duplicate the issue you describe, so I'm shooting in the dark a bit.

The only other thing you might see is people who do black-on-black for spoilers, but again I have no way of knowing if that's the cause.