Thread:Support/Translate-magic-help («Vous pouvez traduire les alias de pages spéciales, les mots magiques et les noms des espaces de noms.

This MediaWiki message says that namespace names can have only one translation:

This is wrong since long, and in fact in almost all cases, the namespaces have several names, the first one being the default displayed (one or more translations, followed by their English equivalents). For example "File:" is the new namespace name but "Image:" is still supported as an alias, and both can be translated. Keeping those aliases facilitates the upperward compatibility of links, and helps the autotranslation of many parts of the user interface.

Shouldn't this part of the message be removed ?