Something else I was looking at today had me thinking about accents. Specifically, that distinctive regional accents develop in the absence of a stabilizing influence from outside. When the BBC developed national service, for instance, they sat down in committee and decided what the definitive pronunciation for the radio service was going to be, creating what has become known as "received pronunciation." In the USA, the process was less formal and centralized, but we almost all speak with what was a midwestern accent, which succeeded the mid-Atlantic accent as America's prestige dialect.
My point? In the post-war world of Fallout, regional accents would have made a resurgence, and certain older ghouls as well as the Sole Survivor in Fallout 4 would "talk funny."
And then there's literacy. The near-universal literacy of modern civilization is a historical anomaly. Learning to read takes time and effort, and is only of benefit to people in certain professions. With no tax base to provide organized schooling, most people in the Wasteland should be illiterate. So... why aren't they? We see the Schoolhouse in Diamond City, of course, but I can't believe that Jack and Jill Raider are raising little Molly Raider to respect the three Rs. So... where do they get it?