Honest question - What DO you merge into shared branches? And, when your local needs to "catch up", don't you have to pull in those shared commits which conflict with your magit-wip commits because they touch the same code, but are different commit hashes?
The magit-wip commits go on a separate branch and ideally I'm never even aware of them. They just disappear eventually. They exist purely in case of a disaster à la the article.
I make "real" commits as I go and use a combination of `git commit --amend` and fixup commits (via git-autofixup) and `rebase --autosquash`. I periodically (daily, at least) fetch upstream and rebase on to my target branch. I find if you keep on top of things you won't end up with some enormous conflict that you can't remember how to resolve.
Feature branches that have been cleaned up and peer-reviewed/CI-tested, at least in the last few places I worked.
Every so often this still means that devs working on a feature will need to rebase back on the latest version of the shared branch, but if your code is reasonably modular and your project management doesn't have people overlapping too much this shouldn't be terribly painful.