AFAIK, your second request is not possible, since the comments are sent to a client when it asks for a specific file. For example: if you set a comment on a file, every client out there will receive your comment when they ask you for the file. If you are no longer a source for the file, then they will not ask you, and therefore there will be no comment. Doing what you want is possible only by setting you as a fake source for the file, which is no good, IMHO.
Regards.