Does this person want "help" with their stutter? I know I hated it whenever my bosses (people in a position of authority over me) gave me it's the "It's ok that you stutter, you are still valued" speech. I have been in a good place about my moderate stutter my entire life. So it always felt that speech was more about them accepting that I stuttered more than trying to make me feel OK about my stutter. But it was always a burden when having to let new people adjust to it in the workforce. Like a stutter is something to be ashamed of and they were showing they were good people by telling me not to be shy or ashamed of myself. And as for when I'm stuttering, I'm in my 40s now. You will wait for me to finish speaking. Nothing more irritating than having someone fill in your words, unprompted. And stay focused on the person while they are speaking. I would treat them exactly as you have been before; like a person, not a stuttering person. And it's good you are showing concern, there is that personal/professional line. And the question is "Does it affect the work?" OR "Do think they would be more productive without a stutter?" I've also had "I thought you were mentally challenged because of your stutter, but you are actually really smart" from my bosses, so . . . . . .