> If there's ever a time when you're not signed into any device, you have to reset your encryption key, meaning you lose access to all old messages...
That is a deal breaker, IMO. Encryption is great, but it shouldn't come at the price of data loss and a degraded user experience.
And there's the whole thing where you have to always be signed into at least one device at a time. If there's ever a time when you're not signed into any device, you have to reset your encryption key which means losing access to all old messages plus sending a notification to everyone you're in contact with. And I've had times when the reset button also just didn't work, throwing some error, so I was just locked out.