Originally Posted by
mr_bill
Wearing a helmet makes it more likely that you'll bump your HELMET in a fall compared to not wearing a helmet in a fall. That's not a bug, that's a feature.
-mr. bill
At the risk of belaboring the obvious, when you bump your helmet, you bump your head inside the helmet. Your head experiences an impact. You aren't bringing up any new point in this discussion.
The valid point that the other person was making, is that the impact ("bump your head") is more likely given the extra width of the helmet. I stated at the outset that while it IS more likely, it remains to be proven how damaging those impacts are in practice vs the mitigation that the helmet provides.