I have tried using the "Embed Multimedia Content" button in the knowledge article editor and I have also tried creating a visualforce page with an iframe and embeding that into the article. None of the videos will allow fullscreen playback. I have also tried vimeo. Anyone else run into this issue?
That didn't work. I noticed that after I saved the article, it stripped out some of the allowfullscreen code I had used from the article you mentioned above. (i.e. webkitallowfullscreen="webkitallowfullscreen"). We are using chrome in our org.
