As a stutterer, I would say that it’s kind of pointing out the obvious. I don’t know that I’d necessarily be offended as I’m older and realize people are curious. However, envision every person you encounter noting your whack widows peak or pigeon toe (those are terrible examples) something you may be insecure about and have no control over, it would be tiresome. So yea just maintain eye contact; I’m sure he has something to say, that’s worth the wait.