>> mp_units::quantity<mp_units::si::degree_Celsius, double>
> OK, that type exists. How does it support your assertion that there exists an mp-units computation where the result contains a unit that is not found in any of the inputs?

It doesn’t, I was just addressing the point that units are explicitly written. It was not my assertion to say that in mp_units of Celsius and Kelvin are link somehow, because they aren’t.
Sorry if this was a misunderstood.