Web: alternative opt-out mechanism

[snarfed]

We currently let web users opt out by adding #nobridge to their profile/homepage or by emailing us. I don't have numbers on how many sites do it via #nobridge, but more and more have been emailing us to do it, particularly more traditional (and often bigger) web publishers, 10-20 per day right now and growing. Opting them out manually only takes me maybe a couple minutes each, but still.

I'd like to figure out a self serve way to allow this that doesn't require them to change text on their home page, but still checks that they actually represent/own the site. Traditional domain auth via eg DNS or /.well-known/... are definitely too technical and heavyweight.

The one idea I have is setting up an automated email address that checks DKIM, SPF, etc, and then allows opting out a web site if the sender's address is on the site's domain. Not ideal either, but maybe it'd work?

[snarfed]

Alternatively, a simpler, dumber idea here would be to just not require auth. We let anyone bridge a web site; maybe it'd be ok if we didn't check that it's them disabling it?