Oops, I just realized that my example implementation of
make-reversed-comparator is incorrect, the below should work though

(define (make-reversed-comparator a)
  (make-comparator (comparator-type-test-predicate a)
                   (comparator-equality-predicate a)
                   (if (comparator-ordered? a)
                       (lambda (x y)
                         (>? a x y))
                       #f)
                   (and (comparator-hashable? a)
                        (comparator-hash-function a)
                        #f)))