> If you remove the communication links between those nice round planets shown in the animation, they become drab and dreary, and not worth having at all, and you're back to twitter.

True, if you are the toxic community that was cut out. You know who still thinks the Mastodon is worth having? Mastodon.social users, who were able to protect themselves from unfriendly/unwelcome users, and didn't have to go back to Twitter.

Also, you gave an extreme example, of a left-leaning and right-leaning instances not agreeing with each other. But I see no reason why an instance mainly populated with geeks and an instance mainly populated with gamers/musicians/sport fans can't peacefully federate.