Last modified: 2014-11-05 17:50:18 UTC
Sitenotice is always displayed in site language, never displayed translated (when user has different language set or using uselang= parameter in URL query) although translations exist.
It seems to me this behavior is a relict from fundraiser central notice, IIRC translations for sitenotice worked before it.
Actually, the fundraiser's central notice is the *only* sitenotice implementation we've had that used the user's language. :)
Since we're currently *not* using it, it's back to the heavily cached local notice which uses the content language.
Isn't this either bug 1495 or siblings or just a use case for [[mw:Help:Extension:Translate/Unstructured_element_translation]]?
$wgForceUIMsgAsContentMsg can be used as a workaround.
bewikimedia make use of this to make the sitenotice display the translations.