i have removed the youtube markup (BBCode) and replaced with the automatic Simple Audio Video Embedder.
every site is different but it does provide extensive support and can be used, with a bit of fiddling, with Soundcloud and many others.
i suggest trying the original URL with any site that has a built in player but i can't guarantee that it sill support everything. as an example, for embedding youtube clips, just copy the URL and change the "https://" to "http://".
sorry for not announcing this earlier and the Embedder is constantly being upgraded so what didn't work today then may work tomorrow.
i want this forum to be as media-friendly as facebook but it is an ongoing project.
i will publish such changes as often as they come to hand.