Agree about privacy.
By the way, Amethyst (or any other client, I guess) can provide to any npub a shadow ban. Easily. Relays will eat your events, but clients won't show it to anyone.
For example that's how Amethyst spam filter is working - blocking npubs without your participation, automatically. Default settings. Read the thread:
The same about relays' spam filters. I think it may mark any account as a spam at some point and stop delivering content to other users. Maybe not all of them at the same time, but it is possible.