@simon_brooke Search indeed has to be opt-in (as it already is for server-local search).
I’m fine without algorithms and better discovery and it’s awesome that the Fediverse doesn’t need a firehose (=global view, like Bluesky needs).
But some people find it difficult to find interesting content and accounts. Fediverse search engines can help them.
@rauschma some sort of cryptographically signed key ought to be possible. It would probably be very difficult to devise a scheme of reasonably compact keys that would guarantee that two different users could ever generate the same key, but you could make is statistically very unlikely.