Part of the complexity is if I format my code and commit it, and then you checkout and make a change, we don't want your formatter to have different opinions on

Part of the complexity is if I format my code and commit it, and then you checkout and make a change, we don't want your formatter to have different opinions on how to format my code. For this you need (partial) stability at least across minor versions, which is harder with a less-explainable algorithm.