My rule of thumb with mute characters, or ANY character with a disability... hell, you could apply this to any character flaw in general... is that the disadvantage is NOT the character. If all there is to the concept is "Bob can't talk! Pity him!" and nothing else, then the character will come off as one-dimensional.
A disability isn't what makes a person. It's about what the person makes of the disability.
A disability isn't what makes a person. It's about what the person makes of the disability.
