Rabbits certainly spend much of their time grooming, either themselves or a bonded partner. It keeps their fur in good clean condition. Bonded partners also can reach bits that the rabbit might find difficult to reach.
Things to watch out for are if the rabbit is incessantly grooming the same spot. This could cause soreness and also could indicate that there was a problem in that spot. Also when the rabbit is moulting, it will try to groom to excess fur away. They usually ingest this which can cause digestive problems. A good supply of hay will usually ensure that the fur passes through the rabbit without problem.
Otherwise I would be happy that the rabbit is grooming itself. I think it is also somewhat therapeutic and relaxing.
