Here's the working html link. Here's the exact same code pasted into the HTML portion of a page node.
Does anyone know what might be happening within XenForo that prevents the code from displaying as expected? Also, anyone know a workaround?
FWIW, I have just tested by creating an iframe and that does seem to let the viewer render. As the size of the "online viewer" is dynamic, iframes isn't really the best solution though so I'm still curious if there is something not supported in the HTML portion of pages.