As the text in MediaWiki:Mainpage is used as both the link and the link text,
moving Main Page out of the main=dictionary namespace to avoid it being listed
as a wurd, means the link text also comes to include a namspace.
(A detail is that the namespace in question WikiWurdbook: is a pseudo-namespace
at the moment. It might be that real namespaces are stipped for the link text,
but evenso this would be a consistent solution.)