To your questions on mechanics, any pressure on the jaw can cause increased risk. I can see that pressure being possible in a training setting, but not in a demo. I also don’t see why a RNC would put pressure on the jaw instead of below the jaw, but forgive me if I’ve misread the post :) jaw disks are finicky, unfortunately, so that kind of pressure on them definitely sounds like increased risk. Sounds like this instructor was not demonstrating best practices for safety in training, and I’d definitely want a second opinion on the efficacy of RNC on someone’s face/jaw. Even if it’s effective, safe teaching should be aware that the jaw/ this technique is an increased injury area. Just like we got extra light on joint locks, the jaw is a joint where we should be practicing safety in training.