Every paragraph has an \"edit…\" entry in its menu, whether you wrote it or someone else did. It opens the form with the current text; publishing makes a new version that keeps the paragraph's identity, and the page shows the newest version by any member. The earlier version is kept, listed in the paragraph's version history, and can be restored from there.

So a correction to someone else's text is made the same way as to your own. Nothing needs the original author's key, and nothing is lost.