Manual:$wgForceUIMsgAsContentMsg

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

For example, for regular Wikipedia sites like en, there should be only one 'mainpage', therefore when getting the link of 'mainpage', we should treat it as content of the site and call, while for rendering the text of the link, we 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 $wgForceUIMsgAsContentMsg = array( 'mainpage', 'portal-url' );