Madtown and Frozen,
Just a quick internet search fully supports your posts and blows any credence Piney claims on this subject.
The Merck Manual
Traumatic causes of TM perforation include
Insertion of objects into the ear canal purposely (eg, cotton swabs) or accidentally
Concussion caused by an explosion or open-handed slap across the ear
Head trauma (with or without basilar fracture)
Cdc.gov
A concussion is a mild form of traumatic brain injury (TBI) caused by a bump, blow, or jolt to the head. Concussions can also occur from a fall or a blow to the body that causes the head to move rapidly back and forth. Doctors may describe these injuries as mild because concussions are usually not life-threatening. Even so, their effects can be serious.
Healthline:
Assault can lead to a head injury. Being kicked, punched, or struck in the head can cause a concussion, closed or open brain injury. Damage varies with the force of the assault.
And this last on relating to actors...
Weapons of Choice
ContactStage Slap
From an on-line conversation I had with an advocate of contact stage slaps. This was my response
( FYI: since this was originally posted, more information has come out in medical journals indicating that during a slap, the brain moves violently against the skull, and can cause coup injuries. These can cause bleeding and sub-concussive brain cell damage.)message to morgan46@ehow:Thank you for your e-mail. I still want you to consider revising the way you teach the stage slap.I agree that most of the time the contact slap works. But it is the one percent of the time when it doesnt that worries me, because when it goes wrong it goes horribly wrong.Here is a more full explanation of why I am so against it, followed by a detailed instruction of how to do a non-contact slap:There are some stage combat experts who insist that an actual contact slap to the face is perfectly safe as long as it is modified slightly. I have seen videos sold by these same professionals showing actor/students facing each other and trading slaps back and forth to prove the safety. Those experts are wrong. The contact slap is inherently unsafe. The slap to the face sends more actors to hospital emergency rooms every year than all of the other techniques of stage combat combined. This includes knife fights, broadsword fights, swinging from ropes, gunshots
all of the other techniques of stage combat combined.