Hmmmmm... then someone in TSA "management" should check DEN's checkpoints. No scribbles, etc. there; TDCs just stamp the BP with a round "stamper" that has a "print" radius of about 1/2 inch. Wonder how they audit that the TDC was doing the right things?
It is not necessarily standard across the board, some airports have different ways of marking them. Many airports just use a scribble (we do) to mark the BP as a part of the process, sort of like ticking off things on a checklist. Name, date, locations, time, etc.