Lots of people complain about head shots from reds. lots of people have complained about being injured from red shots to the head, myself included. what can we do to address this perceived issue with our sport? do we need a change in some of the rules language? Is this something that we need to encourage classes on to encourage a change in culture?
Unpopular opinion: Red Certification like SCA-style authorizations. Have players re-certify every few years to maintain authorization of Red usage.
More acceptable solution which is not specific to any particular melee weapon:
One Unintentional/Accidental Headshot = Player takes death
Multiple Unintentional/Accidental Headshots = Player is removed from field
Any/All Intentional/Malicious Headshots = Player is immediately ejected from the field
Repeat Offender(2nd time) Intentional/Malicious Headshots = Player is banned from the game.
My only issue with how you worded this is when an accidental headshot was caused by the defenders actions. I have definitely been hit in the head when I ducked my head into an incoming shot.

Fair enough. Head blocking is easily more prevalent than high noons, especially in the newbie category. People are often afraid of the weapons and move their bodies away from the combat, leaving the most delicate and precious part right in the way of the swings. Those folks are the ones we tend to pull off to the side and go through some basic fighter movements with again.
What has surprised me is how many places DON'T teach their new fighters even the most basics of things. It's something we've always done, and we do even more when we work with cross-gamers. .
As CY stated, authorizations along the lines of what SCA does would do a bit in helping get trained red users on the feild and not John Doe with a big stick, but to be fair across Dagorhir as a whole we would probably need to add authorizations for ALL weapons styles, which would be a bit difficult to get set up and be universally run and tracked.
You will never be able to 100% control what happens on the field. If the possibility of head shots is of particular concern (such as myself I find people hit my head trying to reach over my shield blindly but hey I'm 6'5") I recommend a good steel helmet. Then you need only chuckle quietly to yourself when your head makes a bell sound when struck with a full force red shot meant for someone else.

Of course you can't control 100% of the field, and this IS a combat game, so accidents will happen. However, based on our own rules(MOA), heavy injuries should not occur through the regular use of our weapons. Having experienced a great many, I promote the use of general safety gear to ALL players. Cups, mouthpieces, knee pads, lax gloves, and safety glasses/goggles are all considered standard equipment. Unfortunately, there are no reasonably-priced, market-available equivalents to medieval helmets. Some players have started wearing caged commercial sporting helmets out of concern for continued head shots following received head injuries. While it may sound cold, I am of the impression all safety equipment should be able to generally blend in, and no safety equipment that is both overly obvious and doesn't meet the garb standards should be allowed.
What helmet resource(s) might you point players to who are concerned about head shots? .
I like the idea of a rule that Red wielders take a death after hitting somebody in the head... In theory. In practice, I think we would see a certain type of player who intentionally blocks red swings with their head, because it doesn't do them any game damage and kills the red fighter.
I'm more in favor of proper red training, and watchful heralds who pull dangerous fighters.