I think their justification for the charging port on the bottom of the mouse has some legs. They state that the cable is not designed to handle much stress around plug and they've assumed that given convenient location, users may be tempted to leave cable connected at all times making it prone to premature failure. So they've opted for short "usage down time" instead of that.
> Incidentally, why is the degree immune to disappearance in division unlike all other units?
It's not. If you divide temperature by temperature (T/T) you get unitless value. But it doesn't make sense (what does it mean Kelvins per Kelvin?) Your mistake is to take a scalar value for temperature: 300 K / 2 = 150 K (T/scalar = T).