Yeah that's a gag I have used when I really want to be sure its impossible to swallow the mouth stuffing. I consider it very safe. Also can wrap tape around with very minimal sticking to the tiny hair ends which stick thru the tights.
Try mine sometime: push the panty portion into your mouth, wind the legs in opposite directions around your head while stretching them, wind between your teeth, next pass they'll fill and cover your mouth, and tie behind your head. EFFECTIVE!