[jeroenhd]

There is no technical reason why migrating between homeserver software doesn't work, there just is no tooling for it. Someone could build a Dendrite-to-Matrix exporter+importer. The protocol itself doesn't really care about what server software you're using.

I don't know any good messenger that doesn't tie their accounts to something portable. Plus, I think the ability to reset your password/passkey/whatever if you forgot it is way more important than having users manage their own identity roots for any serious messenger. The alternative is very cool, technology wise, but not really something I would care to use and maintain.

For users migrating accounts, there was a tool (not sure why it died) on the Matrix website that would log in to both accounts, go through each room and where possible invite the new account, and leave with the old account. As long as you have invite/join permissions, that's all you need to do for most chat rooms. 1-on-1 chats need some extra commands to set the metadata right so clients recognise them for what they are, but even they can be ported over, mostly. It's not a perfect solution, but it's lots better than nuking your entire account and starting over from scratch.