MAN pages which exists in other places(draft)
In Fedora-devel mailing list  Rahul Sundaram makes attention to existing Debian policy to write man pages to any packages. I generate idea what it will be cool to propagate something similar to Fedora guidelines. So, with big help of Rahul Sundaram ,  I'll try to do it.
After section Documentation guidelines I offer add next paragraph about mans:
If additional useful patches related to man pages exist in other distribution packages the package maintainer should evaluate carefully available man pages. If new package have not appropriate man, or you known where it exists in big quality (ex: often man pages in Debian), add those that are suitable and send them to the upstream project as well. It is highly recommended that the package maintainers consider to write a man page, especially for command line applications where good documentation is missing in the upstream project. If package contains documentation in other formats (like info or plain text) it is highly appreciated to convert it into man format where possible. It might be useful to talk to the upstream projects first and check whether they are willing to accept man pages or other forms of documentation as patches.