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 stays on the network and can still be opened at its own address.

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.