anchor.diff:        (save-excursion
           (with-point ((start (current-point) :right-inserting)
                        (end (current-point) :left-inserting))
  -          (cond
  -            ((buffer-mark-p (current-buffer))
  -             (move-point start (region-beginning))
  -             (move-point end (region-end)))
  -            (t
  -             (line-start start)
  -             (line-end end)))
  +          (set-region-point start end)
             (skip-whitespace-forward start)
             (when (point>= start end)
               (insert-string (current-point) line-comment)
  
positive.code:             (loop
                (when (same-line-p start end)
                  (cond ((space*-p start))
                        (t
                         (insert-string start line-comment)
                         (unless (space*-p end)
  
negative.code:     (when line-comment
        (with-point ((start (current-point) :right-inserting)
                     (end (current-point) :right-inserting))
          (set-region-point start end)
          (character-offset start -1)
          (loop
            (unless (search-comment-start-backward end start)
  