Original bug title:
When entering the URL generated by the Translate extension into my browser's address bar it says: "Translate in zh please."
But when I choose zh-hant from ULS, it allows translating into Traditional Chinese (zh-hant) and it creates the URL, I later tried to enter in my browser's address bar (which fails with "Translate in zh please.").
Here is the URL: https://commons.wikimedia.org/w/index.php?title=Special:Translate&group=page-Commons%3AVandalism&filter=&action=translate&language=zh-hant
Expected: Consistent behaviour.
See also T124013: Do not allow saving translations to blacklisted language codes