Netsplits, missed messages and bot wars over channel and nick ownership were an integral part of IRC UX, and they were direct consequences the IRC protocol. If Discord was run on top of IRC protocol, it would have the same. Discord would probably be its own network and the people who prefer IRCnet, EFnet or QuakeNet would never touch it.
>Like “the UX of HTTP is horrible”? Still doesn’t make any sense
Sure it does, when all browsers have more or less the same, and the context makes clear we're not talking about the mere programmatic consumption of HTTP (like through some REST api).
"But it's a protocol and not a client" is pedantically irrelevant, given that the clients for that protocol all follow the same conventions. The parent already said they meant the UX of it "which is arguably similar between implementations".
Besides, protocols impose some concepts and models of interaction and consumption, which informs any UX created on top of them. So it's not like that client sameness is merely accidental and unrelated to the protocol either.
Discord could well run on top of IRC the protocol and be open to federation without any change of UX.