As to relative safety, I firmly believe that bare feet are much safer than shoes on an escalator. The reasons are that:
barefooted people can feel and are aware of where their feet are at all times,
barefooted people are acutely aware that the moving parts of an escalator do have the potential of doing damage to feet, and
barefooted people aren’t lulled into the false sense of security that a shod person might get as a result of seeing the “No Bare Feet” signs, and so are extra careful.