6  Use HTMLFilter
13-14  Any incoming request to /_comment/ we handle internally
   16  Request other than /_comment/:
   16  Let the request be filtered by HTMLFilter
20-24    Before </body>:
   26    Add any comments associated with the PATH_INFO
31-38    Add in a form that submits to /_comment/ with path_info=PATH_INFO
   40  Requests to /_comment/ go to comment_app():
41-43    Get the variables "comment" and "path_info"
44-45    Save the comment into a dictionary keyed by path_info
46-49    Redirect them back to where they came from