We regularly¹ have unclean merges at my company, and I consider my coworkers competent, and well above "the bar". The biggest problem we have with clean merges is that nearly every CI system & code review tool out there doesn't test the final product — the merge commit — until
after it is merged. GitHub follows this flow by default, and usually even with more CI tooling on the side. Something like bors-ng is what one has to adopt. (And we're struggling to do this for our monorepo due to other points the article touches on.)
While it is possible (if difficult) in git, some VCS systems struggle even harder with this: Perforce and derivatives, for example, simply can't, by design, perform atomic test & commit.
¹like once a month, or so, over the whole company
