Quote Originally Posted by Radar View Post
I do not think that it needs to be too complicated and most likely was already solved by someone. As far as I would say, most likely the emited radiation is nicely random and isotropic but only in the rotating frame of reference of the black hole. If you go back to any inertial frame of reference it will naturally show that the radiation carries a non-zero angular momentum. This makes additional sense since a rotating black hole drags the surrounding spacetime in its spin.
This is a pretty good way to look at it.

Also, Hawking Radiation values over the entire lifespan of a black hole can only be approximations given our current knowledge of physics. Once the hole gets small enough, we'd need a full theory of quantum gravity at least, and probably a full theory of everything to get precise values.

However, it's a pretty good bet that Hawking radiation still happens through a complete decay process, even if we don't know the exact rates. Also, it's a pretty good bet that frame dragging or something approximately close to it happens through the whole process. So, the evaporation process will probably carry away angular momentum through the entire decay timeline(which probably proceeds through to 0 mass with one last quanta or pair of quanta emitted,) even if we don't know precisely how fast that process will occur.