Thread:Project:Support desk/Article names only numbers with length of 8 or 13/reply (23)

If i'm right, you can not return a status except true or false :) But you can add a text to the content. If you want to do that without message keys (like you try in your example, then use OutputPage::addHtml.

If you want to use wfMessage you must define an localization file in your extension setup and use the messages keys, look here: https://www.mediawiki.org/wiki/Manual:Messages_API

This messages you can add with OutputPage::addHtml.