- Open Manual:Upgrading at mediawiki.org and follow the "Translate this page" link for any language except English.
- Check unit #111. The English string contains a <br/> tag.
- Try to translate the string.
The extension keeps complaining about the <br/> tag and won't accept a translation with the tag in there - you can try and save the translation anyway, but the translated page won't be using the translated string. Of course if you don't use the tag, the result is mangled...
Feel free to reassign to a doc maintainer if you find one.