Sorry Till, I thought Falko may have been checking I didn't have some other problem in the file.
When I do this as expected it complains about the directive I set in error:
Syntax error on line 27 of /etc/httpd/conf/vhosts/Vhosts_ispconfig.conf_25-03-09_07-46-27:
URL to redirect to is missing
Still its not #'ing out the lines in the directives box.