I was thinking of WoT by allowing up to 2 or 3 degrees of separation.
If you found a bot or bad npub, the client would tell you which WoT chain allowed you to see it and you could then manually distrust that contact.
It's known that you are connected to everyone else in the world by 7 degrees of separation. So choosing 2 or 3 as default, should be more than enough to break any echo chamber.