User blog comment:Rappy 4187/Technical Update: November 18, 2015/@comment-4129195-20151118234812/@comment-1757994-20151119004337

It's a MediaWiki thing, not a Wikia thing. If an article is organized hierarchically, and if the title is H1, then everything that falls below the title should be other than H1. Just think of it as a quirk that MediaWiki allows =Header= as wiki markup and actually renders it.