In the auto-commentary to The Fourth Council, the Omniscient Dolpopa asks the proponents of self-emptiness (rangtongpas), with folded hands:
How is the realization that everything is empty of self not the same as no realization?
How is the explanation of everything as empty of self not the same as no explanation?
How is stating that everything is empty of self not the same as not stating anything?
These are not merely clever questions with a polemical intent. They are sincere questions that every advocate of the rangtong view must answer to his/her own satisfaction, or else abandon that view of radical self-emptiness, which is either dangerously close (and thus leading) to nihilism, or nihilism itself.
If everything, including Buddha nature, were self-empty, then there would be no difference between the absolute and the relative.
While advocating neither, the Protector Nagarjuna warned us that nihilism is worse than eternalism. The Great Madhyamaka is neither nihilist nor eternalist. It is the Great Middle, beyond all extremes.
Buddha Nature is empty of all that is imaginary and dependent, and it is full of the perfect qualities of ultimate reality: True Purity, True Self, True Bliss, and True Permanence.