Add some text to the end of a page.
Steps to reproduce:
- Open a page that happens to contain interlanguage links (i.e., links to matching articles in other articles; not everything is at Wikidata).
- Put your cursor on one of the convenient blank lines at the end and start typing.
- Check the wikitext to discover formatting problems like https://fr.wikipedia.org/w/index.php?diff=prev&oldid=106426239 where the interlanguage link is now located inside the new section heading.