[mr_johnson22]

Self-hosted Matrix servers still incur the risk of leaking metadata to whatever other servers it federates with (which of course isn't a problem if you don't federate, but that kind of defeats the purpose of using Matrix in the first place).

IMO that's an acceptable tradeoff for achieving decentralization without making the protocol overly complex (AIUI something like Signal's "sealed sender" system doesn't work in a decentralized environment)...but it still feels like a nagging threat that needs a proper solution eventually.