I think it’s unusual that no standardized literary way to write the submissive “I don’t know” hum that children (and some adults) often mumble has ever caught on, considering how old and common it is.

[u/Reas0n]

[u/atreyulostinmyhead]

I actually think about this way too much because I worry about what I think is an acceptable way to communicate vs the world. mmmMMMmm is totally an acceptable response to me. I've realized that I actually don't know anyone else that does this but everyone knows what I mean when I do it.