My feeling is that whether it is disrespectful or not depends on your mindset going into it. I suspect you will learn quite a bit from watching peoples facial expressions and their general responses when you stutter. It’s interesting to think about doing this in other contexts though. Using a wheelchair when you don’t have to would probably be similarly informative (I suspect you would be shocked at how many people look at you with pity). This doesn’t seem that much different than the fake stuttering case. But if it gets escalated to pretending you have cerebral palsy or something (more “acting” involved) then I feel more uneasy about it. Given that you’re acting with stuttering as well, I don’t totally understand why I feel this way but I do.