You should use warm water when you're washing your hands.

Why?

I'm already upset enough about what the water heater water is doing to my skin and am about to go tankless under my bathroom sink!

That's by far the more practical option anyway if we truly cared about the problem instead of fawning over engineer porn. The problem is solved. This is pointless engagement about temperature preference masquerading as something more interesting.

It used to be public health recommendation (bathrooms in commercial buildings will often only have warm water, for example, because code required it).

There's been studies demonstrating that soap is what matters.

Solubility is a function of temperature.