That is just blind bad luck. I looked at the code and I was not joking when I said it ignores IGNORABLE:

(defun collect-ignored-args (declarations)
  (loop for declaration in declarations
        append (loop for decl in (cdr declaration)
                     when (eq (car decl) 'cl:ignore)
                     append (cdr decl))))

Note that (declare (ignore)) works fine, so I think (declare (ignorable)) will go  in the right place if it is not ignored. By the macro. <g>

kt