You speak in a language too cryptic for regular consumption ;)
Which "Fediverse"? As I understand the concept, it applies to social networks in general. But it appears that you are referring to one specific network which contains the Gab server in it.
"Fediverse" = federated universe. Basically a bunch of smaller social networks speaking together through common protocols. Think: being able to follow a YouTube channel straight from your Twitter account — no need to create a YouTube account.
The most popular of such networks is Mastodon (https://joinmastodon.org/), which everyone can run on their own server (often referred to as an "instance"). By default, you create an account on one server and just speak to everyone like if you were on the same server. If one of such servers turns out to be a cesspool full of bigots (like Gab is), an admin can simply say "my server will no longer communicate with that server". When a bunch of servers do that, Gab is pretty much isolated, even though it's using an open protocol.
To put it in layman's terms: if a lot of spam comes from user@example.com, Gmail can just dismiss the emails coming from all addresses that end in @example.com.
Server owners are usually transparent and keep lists of servers they're not speaking to on GitHub or somewhere.
Which "Fediverse"? As I understand the concept, it applies to social networks in general. But it appears that you are referring to one specific network which contains the Gab server in it.