I think the last one of those I saw was Advogato? Some of the social media systems, including Bluesky, started as invite-only, but that was only ever really fo

I think the last one of those I saw was Advogato? Some of the social media systems, including Bluesky, started as invite-only, but that was only ever really for rate-limiting and in particular there were no negative consequences for inviting someone who was subsequently banned.