Don't agree.
The reason most forums dont allow much user definition in the layout is quite simply because the users are so stupid.
Why don't we have user-defined fonts while we're at it?
Nothing looks better than white comic-sans text on a white background.
Such flexibility only serves to create a support burden with no benefit.
One thing to consider is that Piano Street does it right on a per cent basis with the default settings. This doesn't mean it is right for every user, but for most users reading lighter text on a darker background is less eye strain than the other way around (for print though, which is reflected light, darker text on a lighter background works better). Of course, this is only for most persons studied. There are exceptions with some persons though . . . and also with some hardware. On a Mac this website is far brighter than with a Windows system, which could cause an issue with the high contrast than with a Windows system. But don't professional websites detect browsers, O.S., et c., and adjust accordingly? I think that for a professional website it is good to try to accommodate as many users as possible, and this is a website with areas of paid access and presumably also professional staff with that level of expertise.
I think there might be ways to hack one's own system so that certain schemes appear no matter what the website . . . maybe this is something to look into as well.