Other than backwards compatibility with previous IRC clients, is there anything IRCv3 brings that something like Matrix doesn’t do? Despite myself being a pretty prolific EFnet’er 15-20 years ago, most of the world has moved from IRC and I question the value of splitting resources across too many different efforts, when I think we’d be better off if everyone adopting a federated protocol like Matrix; which I believe covers pretty much all of the IRC use cases in addition to a number of others.

Yup, specifically a base64 image encoded inside a Markdown document.