There may be a misunderstanding then Thérèse; the GNU Webmastering Guidelines had never asked for the Webmasters themselves to write to the list. https://www.gnu.org/server/standards/#distros #3 has that the requestor (not the Webmasters) write to the list after the Webmasters have verified (in #1) that the people requesting are the primary developers and (in #2) briefly checked that the distro is a feasible candidate.
> By the way, I wonder what webmasters have to do in this > process, except acting as spam filter. That is effectively it, yes: To make sure that the people asking for the endorsement are the right people, since only the primary developers can request endorsement -- the users of the distro should be referred back to the primary developers -- and to filter out distros that clearly (based on only a brief examination) won't qualify.
