as long as you have a formatting tool that can work in-memory on entire files (treefmt with the right configuration achieves this, clang-format can do it, nixfmt can do it, etc.) you can jj fix -s X on any X that has formatting-related conflicts (e.g., from a rebase or merge or revert) and the remaining conflicts in X and its children will be exactly the non-formatting ones. (jj fix -s X is also the tool that fixes formatting in X and its children in the absence of any conflicts)

I wouldn't call this a Jujutsu perk though because as I said the exact same results can be achieved with Git and insofar as it is more awkward to do so it is only the usual Jujutsu–Git delta of awkwardness