Board Thread:Support Requests - Getting Technical/@comment-28083312-20161226151128/@comment-9605025-20161226223200

I haven't worked with embedded items yet but the thread you linked to is 3 years old. Since then, there has been further restriction on the types of pages that can be edited. I would not be surprised if the MediaWiki namespace was included in this. Also note the iframe is not included on the list of available HTML tags.