One reason to include blockchain tech in games is to enable trading of in-game assets without needing to build a trading engine from scratch. It also offers the chance to tie in-game assets directly to real-world values, and have certain assets be useful across games in a franchise. Basically everything Magic The Gathering or Pokémon does, except that you don't have to worry about the cards deteriorating as you use them.
Once you realize that Magic and Pokémon were just cardstock NFTs all along, the whole idea of NFTs in gaming start to make more sense. Not every application that the the Crypto Bros propose to solve with NFTs are really appropriate, but some are.
I think federation is overrated. How difficult is it to have multiple accounts these days?
It will be very hard to vet users from other instances properly in the Fediverse. Even if tools exist to do better validation (like, for instance, allowing an instance to validate that the subscriber from another instance has a valid email address), someone with ill intent can figure out a way around that.
I think that the Fediverse could use an identity verification service, but fear that's what Facebook is trying to be.
This was in fact the original purpose of cryptocurrency. The seminal Bitcoin white paper is titled "Bitcoin: A peer-to-peer electronic cash system".