I think this is done systematically in Reddit, for example, where typos are inserted in reposts to bypass detection. A lot of the frontpage is riddled with creative typos and grammatical errors.
I had a voicemail last week that had a lot of "ums" and "ahs" in it. It wasn't immediately clear that it was a robo-call, and then it became a lot more interesting because I could tell it was computer generated woman's voice.
