Michael Catanzaro commented on a discussion:
Both Bart and Andrea as well as Emmanuele expressed concerns about anyone being able to create a :gnome.org Matrix ID. I’m guessing the threat model is that somebody could impersonate GNOME Foundation members.
I think it's way too late to change that. If such a policy were desired, it should have been instituted long ago, before we asked Element to create the dedicated gnome.org Matrix instance for us. I guess hundreds of non-Foundation members have :gnome.org IDs already (would we disable these accounts?). We currently strongly recommend these over using :matrix.org IDs due to serious performance issues with matrix.org. If we stop allowing new registrations, that's what everyone will use instead.
This isn't like email, where the domain implies some formal association with GNOME. I think nobody expects that your :gnome.org ID indicates anything more than choice of homeserver.