It's difficult to see the value in spending time on Mastodon, compared to other services. For example, just checking joinmastodon.org gives the following top 10 recommended options: " GENERAL INVITE ONLY snabelen.no Ein norsk tenar for den desentraliserte sosiale media platformen Mastodon Get on waitlist 1.8K GENERAL INVITE ONLY mastodontti.fi Tämä on suomenkielinen Mastodon-instanssi. Julkisten päivitysten tulisi ol…
Different between Mastodon and the other platforms you linked is that Mastodon facilitates communication between the various instances (if they agree to that). So you can join instance X and still communicate with people on instance Y, and it's easy for the administrators to set that up. It's possible with IRC/Discord as well but it's hacky and requires "bridges" while that functionality is "native" in Mastodon.
It seems counter-intuitive to moderate based on "which server user is from" too.