Glad to hear you enjoyed it :)
> do I get any benefit from the change id if I push to GitHub for PR review?
As of right now? Not really. The details are more complicated, but basically, if your project doesn't like the behavior of github when it comes to comments + editing commits, and wants you to tack on new commits instead, we can't change that behavior. However, https://github.com/LucioFranco/jj-spr can, in some situations, give you some of this experience. If your project is okay with editing commits, then it can help you locally, sure.
However. In an interesting turn of developments, GitHub's new SVP just tweeted that he's likes jj and is interested in adding stacked diffs to github. I don't know how this squares with their "no new features for 18 months" thing, but we'll see!
> But what I’m also really yearning for is having a distributed asynchronous/offline-first code review flow built right in.
It's not code review, it's issue tracking, but I've been using https://github.com/steveyegge/beads this week, and I think it might be the first "put your issues in your repo" system I actually enjoy. It says it's built for AI stuff, but like, you don't have to use AI with it.