refs #1645 : bugfix - comment on comment is properly blocked.

 - Admin panel option did not work on 'comment on comment' function. Now
 it works.
refs #1645 : revert commit for different ticket.
refs #1645 : modified - default comm. action is set to block.

 - Blog creation / new installation set the comments / trackbacks to be
 allowed.
 - Current default action is set to block. Notification is needed.