Manual:$wgForceUIMsgAsContentMsg

List of 1>Special:MyLanguage/Help:System message|system messages that should be displayed in user's interface language, even if they would ordinarily be displayed in site's content language.

Details
When translating messages with  , it is not always clear what should be considered UI messages and what should be content messages.

For example, for regular Wikipedia sites like en.wikipedia.org, there should be only one 'mainpage'; therefore when getting the link of 'mainpage', treat it as content of the site and call   while, for rendering the text of the link, call  . The code in default behaves this way. However, multilingual sites like Commons do offer different versions of 'mainpage' and the like for different languages. This array provides a way to override the default behavior. For example, to allow language specific mainpage and community portal, set