But that is different, as Patriarch Avvakum kept his body intact, and administered a proper confession. Castration is not mortification of flesh -- it insults the Creator.
His rank was Archpriest (monsignor, should we translate). As for keeping his body intact - he must have ended up with a serious burn. In his religious practice he routinely made use of corporal punishment as proper means of penance. And he actually considered that weakness to be a failing in himself, and repented it bitterly...
Can we use chastity belts?