Board Thread:Support Requests - Community Management/@comment-3417079-20150626034226/@comment-452-20150707052230

Templates are basic functionality, and the concept of a or a $1 being replaced is basic functionality.

What you are asking for is advanced functionality.

A 404 error page is not a good example, as a 404 error page is something that is intended to be seen by "everyone". The welcome message mediawiki page is not something that is meant to be seen by everyone, it is only meant to be seen by the admin who is editing it.

A better example has already been mentioned by DEmersonJMFM: Templates.