Worth maybe calling out that there is a few academic language implementations using this name (turnstile, turnstile+) https://docs.racket-lang.org/turnstile. It's not a standalone language but worth pointing out
The lack of some good history mechanism is what has always kept me away from this kind of software. But I don't know how we could possibly get the kind of messenger I would dream of (secure/encrypted, history backup to cloud, and web app for messaging).