[Arathorn]

An easy way to describe Matrix is as a decentralised database of realtime conversations, which are signed and replicated over the participating servers. The main novelty over XMPP MUCs is that conversations are replicated equally over the servers so there's no single point of control - it's really more a decentralised than federated model. And yes, it has (beta) E2E crypto too - albeit trying to take the best aspects of Signal (the double ratchet) whilst also making it usable for sharing conversation history when desired between devices, and actually clearly tracking which devices are participating in the conversation. The "slow evolution" criticism of federation/decentralisation is empirically fairly bogus, as long as you structure the layers of the protocol so they can all evolve independently without cross-cutting concerns.

You're right that people get killed based on metadata, which is why it's in our sights in the longer term. But our focus is first on features that make the system actually compete effectively with its centralised counterparts (encrypted decentralised Slack or WhatsApp style use cases), otherwise in practice nobody's seriously going to use it. And secondarily on protecting metadata, especially given there's stuff like Ricochet & Briar that you can use today if you're doing something where you really need the metadata protection today.