People stutter when they're nervous about trying to express themselves, usually when it's become a reflex habit from lack of confidence in speaking. People who stutter are acutely aware of it and usually feel embarrassed about it.
Poor grammar has nothing to do with confidence in the ability to write. It can be the result of poor education, or the result of a false idea that grammar does not affect meaning, or a preference for writing as if speaking so as to create a colloquial sounding and friendly style. People who use bad grammar are usually either unaware or don't worry about it.
This post was edited by inky at January 3, 2019 6:26 AM MST
