The story of the napkin would have been understood by every Jewish person of that day. As far as the Shroud of Turin goes I have not formed and opinion one way or the other. I do know that the image on it did not penetrate the fibers of that burial cloth either they are on the surface only paint and thing of that nature has all been ruled out. So if it didn't penetrate that cloth how can we expect it to be on a cloth that was on top of it?
I don't think I would call it a anecdotal story given the facts that the scripture verifies a napkin was indeed placed about his head/face and then folded and left there to be found it was not tossed aside as the burial cloth was. Also the custom was well known to all the Jewish people.
Keep Looking Up
Forgot this Edessa Cloth. I may have missed it but I don't reacall this being
mentioned in the post at all.