Twitter DMs: “In order to preserve and extend this user experience to encrypted messages, we decided to forgo forward secrecy. We don’t plan to address this limitation.”
https://help.twitter.com/en/using-twitter/encrypted-direct-messages
About Encrypted Direct Messages – DMs | Twitter Help

Twitter seeks to be the most trusted platform on the internet, and encrypted Direct Messages are an important part of that.

@fj @tqbf they want me to pay for signal?
@fj One cannot trust Elmo. In anything. He turns on a dime.