I never said mass and SA were linear; only related. The
I know, so I didn't claim you said that either. I said not linearly to show that it wasn't very convenient for determining the "amount" of emitted radiation.
True, but without a source of additional energy, things cool. And when talking about such objects, their mass directly determines the amount of black body radiation they emit - whether you measure in photons, watts, or whatever unit you choose.
In the transient case it's meaningless to define the radiation in watts because the emitted power is changing with time. But I don't think Preearth was talking about transient cooling, nor the original poster. It's quite an obscure complication to subtly add which doesn't give much insight into the main idea.
Even then, surely it's "thermal mass" not gravitational mass that's important. Otherwise every material would have the same specific heat per unit mass.
So I still can't see what mass has to do with it at all. In the constant-temperature case a sphere of metal will emit fewer photons/time than the same piece of material at the same temperature but spread in a sheet. However the "watts per unit area" would be the same in both cases, and both quantities would also be unchanged if a denser metal is used. Nor would they change if the sphere is hollowed out, reducing its mass but making no difference to the emitted light.
Maybe in biology light emitting things are always transparent, so thicker materials emit more light?? But it's still only indirectly related to mass.
