i have no doubt a go pro may cause some injuries.
a) isn't it the helmet's job to crack and absorb some of the energy. it seems to me the helmet did its job.
b) a go pro migth act as a stress point but ion the other hand i figure the helmet migth diffuse that over larger area not sure wether that is true or not.
c) to me, based on gut feeling and no scientific or kowledge proof, the biggest risk of a go pro is to force an unhelathy rotation of the head during impact that might have more severe consequenece on the neck than jsut the blunt force to the head.
and yet i still often have one...