It is also good to note that what kind of editing your brain does- the standard that people accept for what clear speech is supposed to sound like, what they strive for and hear in their heads- changes over time. There is more than one way to clean up the exact same actual speech stream, and the cultural norms for the correct way to do it shift.
This is made most obvious when comparing dialogue between new and old movies (good ones, anyway- ones that had good popular contemporary reviews; comparing what people at the time considered badly-written stilted dialog tells you nothing). Everybody knows that preferred writing styles change, but movies document the changes in what people consider to be "normal sounding" speech over even relatively short periods of time (a few decades).
This is made most obvious when comparing dialogue between new and old movies (good ones, anyway- ones that had good popular contemporary reviews; comparing what people at the time considered badly-written stilted dialog tells you nothing). Everybody knows that preferred writing styles change, but movies document the changes in what people consider to be "normal sounding" speech over even relatively short periods of time (a few decades).