The resultant 50Hz flicker gives a greater apparent brightness, like
strobed bike lamps for half the power dissipation!

I thought we were talking about a supply to a fan here..... not sure
what it will make of half wave DC even if the LED can cope!

Yup, way back we decided it wasn't the way to go, this is just philosophy.

BTW, someone chucked a googly when they said some fans have a sort of
pulsed control, so the user's "mains on" state is fleeting.

I dunno what you do then....

mike r