This is an interesting question. Is it safe to draw a bow behind your ear? The answer is yes . . . and no.
For some styles of shooting, drawing behind your ear is standard form, such as Kyudo. However, these styles are usually shot with a thumb release. In a thumb release, the draw thumb is wrapped around the bowstring (from inside to out) and then wrapped with a finger or two to lock it in place. Because fairly heavy bows were shot this way, thumb rings were used to distribute the pressure around a wider area to prevent injury.
In a thumb release, the arrow is held on the other side of the bow (if a modern recurve bow were to be shot with a thumb release, a right-handed archer would shoot a left-handed bow) and the string slides off the thumb away from the archer. This causes a string deflection in the opposite direction of the “normal” Mediterranean release. So, instead of the string leaving the string hand moving forward and toward the archer as we are used to, the string moves forward and away form the archer in a thumb release of the string. This is why archers using this technique don’t accidentally rip off their ears when shooting.
Here is a photo of a modern archer drawing a 170# Tartar bow using a standard finger hook (just to show you it can be done). Look carefully and you will see that he is holding the string away from his face (note the shadow of the string). And, do you now know why, boys and girls? Yes, he would rip off his ear if he held a tight anchor. This is why these bows were shot, historically, with a thumb release.
What you sacrifice when holding the string off from your face is accuracy. Keeping a tight anchor, that is against your face is necessary to get your aiming eye into the plane the arrow will be shot in. When your aiming eye is outside of that plane, you are guessing as to your windage. Since the arrow is an ordinary projectile, if you can line up the arrow with your target (in plane, as it were), then your windage is taken care of and the only thing to concern you is elevation of the bow to get the correct distance.
I note in passing that archery was often used as artillery in the Middle Ages. The arrow cloud scene in the movie Braveheart demonstrated this technique. Historically comments on this technique include hyperbole such as “their arrows darkened the sun,” and whatnot. The archers lobbing arrows this way with English longbows (and a Mediterranean loose) often drew to their breasts with their heads turned slightly away so as to not catch their ears on the loose.
So, the answer to this question if you are a coach is “Only if you know what you are doing” which means “No” for all beginner to intermediate students.