Well we already discussed it in the other thread. There are essentially two possibilities, the wounds were inflicted when they were wearing a helmet or when they weren't wearing one. We know that people walked around with healed headwounds from the 7th century to the 15th century. Now I believe it's possible certain polearms are able to damage helmets sufficiently to wound the person wearing it. These wounds could also have been inflicted when they weren't wearing helmets but the relative number of healed head injuries and perimortem non lethal blows make a number of explanations for that unlikely.
Then there are the perhaps somewhat dubious illustrations of battles. Pretty much all the Swiss sources I looked at show halberds penetrating helmets to a small degree, some show less than an inch of penetration while others show a gash multiple inches, some soldiers are depicted as fighting or fleeing with head wounds while others are dead. Then there are a lot of works from the Low countries that include both drawings and tapestries which show similar things. Some men are dead and have head wounds while others are still fighting. Either this really happened or it's a universal art trend in Europe.
The Uppsala battle appears to be a relatively one sided slaughter and almost no person with previous head injuries (veterans?) appears. The other two/three battles are different.
The helmets could indeed be discarded but a number of reasons to do that seem unlikely to have been the cause of the headwounds.
People could have taken off their helmets when fleeing and were then hit by cavalrymen. Could indeed be possible but, at least in my mind, this does not seem 'that' likely when you look at the relative number of people that have healed head wounds and the place were lethal head wounds were found. Horizontal across the back of the head and downward blows on the crest of the skull seems more likely injury patterns if that was the case. The location and the fact that many apparently survived it leads me to believe these wounds were sustained during the actual fighting.
Then there is the size of the healed head wounds which at Dornach were 3 cm on average and not penetrating the skull. If someone strikes me with a halberd at even moderate force and I end up with a small 3 cm gash across my unprotected head then I would count myself really really lucky.
The presenter
http://hroarr.com/fabrice-cognot-bladesmith/ showed an illustration of the King of France fighting/being captured at the battle of
Poitiers.
[ Linked Image ]
While he is depicted as using a sword and
shield he actually used a pollaxe in that battle. But artistic or cultural reasons lead to him being depicted as fighting with a sword, this trend later changed when it was fine to depict men such as him with axes and weapons such as that. The mac bible predates that picture by a century (give or take a few decades) and it is possible the same rules might have applied then. Perhaps especially so because it depicts Christian superhero's. The illustrator might have personally seen battlefield scenes or knew what type of trauma was common but chose to depict axes and maces as swords (though axes are sometimes depicted). The wounds do seem a little extreme though and the fact that they're biblical hero's might be the reason for that.
The artists inability to illustrate how deep the wounds actually were or the perspective could also have led to a slightly over exaggerated wounds.
As far as I can tell this scene represents a few fleeing horsemen on the right side, note that they are wounded and appear very much alive. That said the wound itself shows a man with his head cloven from crown to halfway his forehead. That's not survivable as far as I know.
Look at the fleeing people and the wounds they have.
http://manuscriptminiatures.com/media/cache/m..._large.jpg
http://manuscriptminiatures.com/media/cache/m..._large.jpg