Board Thread:Support Requests - Designing Your Wikia/@comment-2177054-20140228162050/@comment-2177054-20140228165550

It seems like that problem is not in plainlinks, but the gallery itself:

http://spongebob.wikia.com/wiki/MediaWiki:Help_Wanted_(gallery)

Once it is embeded to normal webiste, it acts normally, but on wikia it adds that extra heading.