[pdonis]

> There is a minimum threshold for stellar black holes–the ones created through stellar evolution–it's called the Tolman–Oppenheimer–Volkoff limit.

That limit gives the maximum size of a neutron star, but it does not say an object smaller than that cannot form a black hole. In fact, it is considered likely that supernova explosions could cause an implosion that could form a black hole smaller than the limit, simply because it happens too fast for neutron degeneracy pressure to stop it before the implosion reaches the Schwarzschild radius.