Mensur Fechten

[Cornelius Engelhardt]

Wounds going all the way to the skull bone require a lot of force and a very heavy blade??? Harldy. People get cut to the scalp all the time by simple accidents from even blunt instruments. I've seen scalps cut and torn by volleyballs and boffer toys.
The skin on the human head is tight and thin and full of blood vessels. It doesn't take a specialy sharp tool or a great blow to get to through scalp at all.

JC

Believe it or not, all I can do is talk out of experience.
"A lot of force" is of course relative in this case because your movements are quite limited.
And I guess a heavy mensur blade may be lighter than a heavy rapier blade. I have no experience with the latter so I cannot say what wounds such a blade can cause.

[ColinWheeler]

I've had my scalp split open by a well-hit whiffle ball. A whiffle ball is about as far as you can possibly get from "heavy" OR "sharp". If ability to produce a scalp wound was enough to certify the martial lethality or legitimacy of a weapon or a technique, one of the past Masters would have included the devastating Whifflehau amongst their list of techniques, and you would not be allowed to carry a whiffle ball into a courtroom or onto an airplane.

[Ben Michels]

the devastating Whifflehau

This made my night.