We use git rewriting extensively and do allow non-FF commits. We also have process and tools in place such that master is held sacred (and our live branch is untouchable). Every once in a blue moon, a master branch will get a non-FF, and our tooling is such that we make sure everyone knows it happened.

However, we are a small team consisting of mostly Linux kernel developers, so that may influence the level of trust we put in not screwing things up. We also work pretty much independently; were that not the case, this would get ugly.