Board Thread:Support Requests - Getting Technical/@comment-2020924-20150531065600/@comment-24409505-20150601090718

RansomTime, I think the circumstances could be similar to mine: someone enabled a wiki feature that has a custom namespace (i.e. "Top 10 List:") and then disabled it, the page continue to exist.

I just checked the Wiki Features log of the wiki and it looks like at the moment of the creation of that page (17:57, October 19, 2011), the following features were enabled: wgEnableAchievementsExt, wgEnablePageLayoutBuilder, wgEnableArticleCommentsExt, wgEnableCategoryExhibitionExt, wgEnableChat, wgShowTopListsInCreatePage.

Edit: I just searched a bit info on wgEnablePageLayoutBuilder, it is a feature that allows people to create layouts but is no longer actively supported on Wikia. So it's quite likely that page was created using that feature.