This is only true among mastodon servers that connect to each other. As I recall, most servers would not talk to gab's servers.
Further, once you pick a server, if you are kicked off, you lose all your followers because they are following you@thatserver which you cannot get onto anymore.
Further, once you pick a server, if you are kicked off, you lose all your followers because they are following you@thatserver which you cannot get onto anymore.