It all depends on whether disabling nested quotes is about saving bandwidth, saving database space, or saving scrolling time, or a combination of all three...
Hmm, I don't know whether it would be quicker to just hide it in CSS or to strip it on view before parsing (thus saving some tags)
The main advantage of adding a 'view quote' link/button, is that you can possibly get rid of the option.
Well, it's easy to find nested quotes at parse time, so..?
I also don't know how you'd do it in CSS if it's a user preference because that means it can't really be in the CSS file at all... unless we add a class at parse time to it (which is currently not supported and would make parsing undoubtedly slower)