Hi! I've noticed that when you paste a YouTube video here that has HTTPS as opposed to HTTP, it won't automagically embed it into the post. It also appears that, if you do add it to a post and then you go to edit it, if you do not go to the full editor when you save your changes, the video will disappear. My theory is that for whatever reason, without the full editor it seems to shorten the YouTube URL in the middle of it with "..." So when the changes are saved, so is the "..." change. I dunno, I could be wrong.
Just thought this might be an interesting subject.