The idea of insisting on a "clean" commit history always rubs me the wrong way. In my mind a commit is like hitting Ctrl-S. It's just saving a checkpoint in your work. And the commit history is supposed to show what actually happened, not a cleaned-up story about what happened.

I can see that it's good to be able to see that cleaned-up story, but I don't think the commit history should be that. There should be something else, a meta-statement about a bunch of commits, that summarizes it. But the commit history is still there if people later need to dig into how something was done. I saw some other comments talking about PRs as this unit, which maybe works, but I've always thought it would make more sense if the VCS had a notion of "commit sets" to which metadata could be attached. Then you could either look at such a set in collapsed form, with a single summary description of the whole set, or you could expand it out to look at the individual commits. In theory these could even be nested, although that might get messy and I think even just two levels would be very useful.