See my last post about dibbers (or at least the logger boxes) failing.
wear an unfolded number on your vest. Problem solved.
if you want to be anarchic then don't run in an organised race.
I think it should be the RO call and not a a hard and fast rule Bob.
I have never run vestless but would not stop any others of doing so.
Bofra count the runners out before the event and then back in. More my style and still a sensible committee.