"neutral conversation place for the world"
OK, now we're onto interesting stuff
I don't believe this can happen
Any conversation place is going to be controversial by nature.
nostr:npub1f97weyr6rgc7gewa975yzhlnqhnskg5sl8vaxh908ezvsdydza3s40sks4 is right that free speech is mostly a binary... you either have it or you do not (with a minor prohibition on spam, CSAM, dox, nuclear secrets, piracy, etc).