Intriguing. I have found an interesting corner case, where I believe the Common Lisp standard doesn't have an opinion. I don't think it's really any critical corner case, as I (right now) can't see any legitimate use of the difference, but...

Basically, in the case of the following:

(defun frob (x) (format t "Frob: ~a~%" x))
(frob (defun frob (x) (format t "New frob: ~a~%" x))

does the printed line say "Frob" or "New frob"?

It is, I believe, fully specified what will happen when you do either of (funcall #'frob ...) or (funcall 'frob ...), but out of the two implementations I have tried (SBCL and CLisp), I have two different behaviours. SBCL prints "New frob" and CLisp prints "Frob".

I shall have to ponder this, for a bit, I think.