wrote
Rod Speed wrote

Perfectly possible to design the charger properly so that
it is always completely safe even when something has failed.

Good chargers aren't quite that good.

BULL****.

But designing a charger to stay safe no
matter what fails is an impossibly tall order.

BULL****. It is perfectly possible to do a USB
charger so that whatever fails there will never be
mains voltage on the USB. ALL that is necessary
with the transformer is to use a bobbin that
mechanically separates the coils so that whatever
insulation fails, there is never and electrical
connection between the primary and secondary.