Otherwise, composting is the most natural thing there is. Absolutely everything in nature dies, and mostly does not get embalmed, cremated, etc. Which is another way of saying it composts and gets recycled back into living stuff; some of which ends up in our food chain. Things like proteins are broken down in the process. And that would include prions.
So, absolutely nothing wrong with composting the remains of people. It's a nice ecological alternative to carbon intensive cremation processes or having a lot of nasty embalming fluids dumped into the local environment (which is where it ends up after the body eventually decomposes anyway). Not judging here; but I appreciate people making different choices and being somewhat conscious about not burdening the environment with their corpses any more than is strictly necessary.