As a pro domme that has had about 100 full toilet sessions, no one has ever been badly upset or traumatized that I know of. The closest is when someone requests that I be merciless. Then they literally bite off more than they can chew. It just ruins the end of the scene and their climax. I do warn them that very, very few toilets can handle it being forced especially with pound shits lol. If a toilet goes with My recommendation where I just pay attention to their body language, adjusting the intensity as needed, it is always an exhilarating scene where both parties thoroughly enjoy themselves.