The real-life inspiration for Arsinoé was Russian, much like her husband. Her nationality was changed for the film, so the two characters would have an in-story justification for speaking French to each other.
Throughout the film, the word "fascist" is pronounced "fassist". This is deliberate, as Éric Rohmer explained in an interview around the time of release: the unusual pronunciation is historically accurate, and was commonly used at the time of the film's events, when Rohmer himself was a teenager.
Éric Rohmer had originally intended to use a style similar to that of his previous film, Die Lady und der Herzog (2001), with archive footage in lieu of traditional backgrounds. This proved to be impossible due to the quality of the available footage.