>>8
Common Lisp is already case-sensitive, and merely hides it very well. Case-sensitivity is overrated, and many languages don't accomodate it. Common Lisp technically accomodates it, but it can be ignored in practice.
Why would LISP developers want to maintain these :invert/:preserve cludges when case-sensitivity is the standard in most sane languages?
Most languages are insane, because they mimic C. A language like Ada, which is designed to avoid many common programming mistakes, is also case-insensitive. Anyway, the Common Lisp standard isn't changing anytime soon, because there's no reason to. Every Common Lisp program written still works. This is unlike sane languages, where books just a decade old are outdated.