The rabbit doesn't eat anything that is harmful to your tortoise, however, this just increases the risk of the tortoise getting parasites or other 'germs' from the rabbit. I don't like the idea of keeping tortoises in any other animal's enclosure, be it chickens, rabbits, birds, or whatever. I want my tortoise's 'food bowl' (grazing area) to be clean.
That's what I was thinking. My kids like seeing in the rabbit in the backyard that's why I have allowed it. I will seal up the fence a little bit better.
Also is the same little guy that likes the rocks every now and again.