My point is that it not everyone (newcomers especially) would know about various Fedi instances having a blocklist and some even blocking much popular instances. You are assuming that they would at least read usually large list of blocklist or admins even share the blocklist in the first place and check to see if it doesn’t block the instance which has the user they want to follow and interact with.

Some instance have different rule as well as block other instances which will throw anyone off especially if it a big well-known instance like Mastodon.social which alienate large userbase of Fedi.

May I ask why you want to do that?