Anyway, you are right. But that's more about Ahoy and less about Parley. Parley was just answering the question of "What if IRC was federated, and what if it borrowed some ideas from Salty.im -- DNS discovery + WKID".
> A federated network is a system where independent networks, servers, or organizations agree to follow common standards so they can talk to each other without giving up control to a single central company.
In traditional IRC networks, you end up forming a spanning tree of servers that belong to a common name, "the network". However control remains in the hands of the operators of that network.
To be sure, Discord "servers" are not servers in the sense the word is used in virtually every other context. They are more like group chats that share a hosting location. If anything the hard part for Discord is making them seem disparate enough that someone might rent their "own server".
irc federation is entirely different. with federation client support for multiple servers is not actually needed. those features are orthogonal.