It would be nice if C-cd@, ie the function doxymacs-insert-grouping-comments would also indent the inserted comments (there can be grouping comments inside a class, they need to be indented). So the end of the function would read :

      (goto-char end)
      (insert ender)

      (goto-char start)
      (insert starter)

Also, I find end-of-line and beginning-of-line counter-intuitive, so I've commented them out in my version, but that's probably a matter of taste.