In Illegal Aliens,, scifi by Phil Foglio, there is a scene where UN officials end up talking to a New York city street gang thru an alien ship's universal translator. It mentions the device facing the arduous task of converting English to English.
Reminds me of a time at work where I had to translate between two people speaking English. One was a heavily accented Scot and the other a heavily accented Chinese. They could not understand each other, but I could ... so I translated between the two, since my accent is pretty neutral.