> You can just mess around and make it presentable later, which Git never really let you do nicely.
I'm surprised to read that, because that's how I've always used Git (and GitHub).
That's what I've understood to be good practice with Git, and it was liberating compared with what came before. One of the nicest things about Git is you can throw things in locally without worrying about how it looks, and make it presentable later.
The problem put simply is that git doesn't support concurrency. Even if you use worktrees, git has a global lock for repo interaction.
https://www.felesatra.moe/blog/2024/12/23/jj-is-great-for-th...
I also did that with git, but it's no comparison in ergonomics. For instance, "move this hunk two commits up" is a task that makes many git users sweat. With jj it's barely something that registers as a task.