@Kathrin

"because (centralised networks) can implement some pre-screening during signup. "
" The fediverse signup process is completely unmoderated,"

This isn't true at all.

Servers can ask users to write why they want to sign up, and screen them through that.

Try signing up on https://mastodon.art to see what I mean. They manually screen all new users before accounts are activated.

And this is nothing to do with centralisation or decentralisation, it's something any site can implement.