anytime you have two rabbits together things can go badly.
I've seen colony rabbits with torn ears, bites, and more.
They can be totally fine, and then totally not fine.
I have learned that sometimes things can go very good for a very long time and owners will rarely, if ever see a problem, and then things can go badly quickly.
But I've rescued tons of "pairs" over the years and 9 times out of 10 one of the pair will have scratch or bite marks that their people missed. I separate pairs fairly quickly, the dominant sulks, the beaten up breathes a sigh of relief. So I always tell people, watch them, as long as they are fine, let them be fine. But be hands on, watch for tufts of fur, and separate sooner than later.