I have thoughts along the lines of "The spoken word is ephemeral; once spoken, it is lost, and only memory remains" - "Unreliable Witness(es)"; but written communication is (theoretically) fixed at the moment it is made; lasting, review-able.

So lacking forgery/forgers, written words are more likely to be "Truth", for a given value of Truth. Maybe.

And you could give someone a name, by writing it out for them. If the language was purely phonetic -

Think about the challenge... of role-playing as a Qestir!