Only on the client side.

The protocol itself is fine.

People choose for themselves which clients to use.

But, just a hypothetical.

Say app/play store removes all the clients that don't implement the system amethyst has.

Effectively you're hidden from all new users if just a handful of Devs or influencers think you're annoying, offensive, whatever.

It doesn't even have to be intentional on the part of those who mute you.