I believe, in a funny way, the job of the novelist is to be out there on the fringes and speaking for an experience that has not really been spoken for. ↗
But I stuttered as a kid. I went to classes to help it, and it just went away around fourth grade, when I became more aware of how others spoke, I think. But also, growing up in the South, a mumble is a way of speaking. ↗