Future linguists are going to be dealing with americanised Korean and Chinese. Mandarin and Cantonese share orthography and not much else. I still don't understand how Portuguese and Spanish speakers can understand each other. Farsi speakers tell me Dari speakers (one of the Afghani languages along with Pashto) sound like they speak with a 16th century accent.

Greek has Demotic and Katharevousa. Louis de Bernieres writes in "Captain Correli's mandolin" implying that the English officers in ww2 sounded to the Greek peasantry like Shakespearean actors, all taught Greek in boarding school, but only speaking "high" Katharevousa Greek, not the common Demotic. He does this by using archaic English writing.

English code switching .. is that really that different yo? Yeet me out of here. Valley girl speak.. the list of dialect and pronunciation in contemporary US culture of the last 50 years is immense.