Consider this:
(defmacro foo (x) "docstring" `(,x))
If I press C-U M-q in the docstring it ends up looking like this:
(defmacro foo (x) "docstring" `(,x))
Strangely enough there is no problem with:
(defmacro foo (x) "docstring" (list x))
Cheers, Gábor