Thank you for the compliments.
As of figuring out how to order the letters, the envelope you may have collected is meant to provide a subtle hint on the word these five letters forms. And its content and position in the game world changes depending on the predefined code randomly selected for the playthrough.
Unfortunately, this mechanic has its technical issues too, it seems, as I encountered a player collecting an invisible envelope he wasn't meant to collect, and that "false" envelope had overridden the true one in the description space of the inventory menu.