Pitch black night and your flying under IFR and using your instruments. Technically you could be in VMC. However how often have you flown into a cloud and not realised til your stobes are flashing in your face?
In fact being so dark how can you tell your actually VMC? There may be a cloud out there within 1000ft or 1500m (think thats the VMC requirment). You wouldn't see it til your in it.
Its dark your flying off instruments in my opinion is IF time. this doesn't apply if your flying over Sydney or another large town.