I forget where I read it (maybe from Martin), but one reason I like to `jj new` before I start any work is just because it makes it easy to revert or abandon if I don't end up liking it. And also easy to diff. `jj new` is pretty much 'free' anyway, every time you make an edit you're creating new commits (not changes!) anyway.
Mostly to keep the new changes isolated from the original commit until they're ready, I think. The only time I use `jj edit` is to resume a leaf I left in the middle of something (where I might have used `git stash pop` but without needing to stash).
