//Okay, so I find this all very interesting, so a few thoughts/canon/headcanon re: Lestat’s dialect in French and how his French changed/evolved over the years.
-Lestat is born and raised in the Auvergne, which means his French patois is ‘Auvergnat,’ which is a branch of Occitan, a dialect of mostly Provence. This dialect, if you’ve never heard it, is NOTHING like the Parisian French that most of us learn in school, nor is it similar to what would have been spoken in Paris at the time (18th century). Here is an Auvergnat lullaby, and here is what Auvergnat sounds like, around 4:17. Here is an example of L’Occitane.
-Lestat then moves to Paris with Nicolas, and spends quite some time there (I don’t have my book on me). His French of COURSE would have changed, as he’d have been mercilessly teased for his dialect, which would have sounded ‘country’ to the people of Paris. Personally, I headcanon Nicolas’ old Uni friends making fun of Lestat’s dialect and Lestat forcing Nicolas to help him with his Parisian French, but that’s not canon, just my thoughts.
-Lestat then relocates to New Orleans around 1791, a time when Louisiana actually belongs to Spain. The French that Louis de Pointe du Lac is going to be speaking here is a whole OTHER kind of French, probably colored by a number of things: Spanish colonists, French colonists, and the patois of the Haitian peoples who also live there. You can read more about Louisiana French here. I headcanon that Lestat definitely learned the patois of New Orleans, especially since he lived there for around 70 years. By the time he meets Louis, his French is an amalgam of at least two different dialects, though the French he’d speak to the Marquis would have been Auvergnat. It’s a testimony to the fact that Louis must have immigrated while very young (hilariously, Louis is NOT actually Créole), b/c I highly doubt he’d recognize the dialect.
-Lestat then learns English from, as he calls it, ‘flatboatmen’ on the Mississippi and comic books, which is hilarious, and pretty much accounts for his tone.
TL:DR; I just feel very strongly about language, especially the evolution of each of these characters, and I love imagining how their capacities for language and dialect have evolved.