No, I don’t believe it is offensive. Especially if you are willing to do it in public, because that will take the same courage as someone that stutters to get out there and speak. And that’s commendable. Even people that stutter will sometimes fake stuttering in order to open up a conversation with others about their stuttering. If everyone in the world faked stuttering, I think that would actually help me improve my speech, because I’d be more comfortable to speak if stuttering was normalized Although I would say that the response of stuttering is usually caused be the feeling inside of anxiety, and that can be difficult to emulate without actually having that anxiety. But I would say creating tension anywhere in the body, especially the throat, and holding in your air to then push out a word is the best way to emulate a block. Repetitions are just weaker, less effort full blocks that feel a lot healthier. Repetitions usually begin to happen when the person is no longer trying to hide their stuttering anymore and their anxiety about expression is decreasing. Hope this helps man!