Try putting a http in front of that URL will cause a 500 Internal Server Error when trying to create a topic.
Repro for the user page as well. If I try to post this URL below for a onebox on it’s own line it fails. Posting the link in a line with other text so that onebox behavior is not triggered does not cause any errors to trigger. Occurs here in meta and on my forum. stimhack - YouTube
@eviltrout can we support youtube playlist URLs? Or at least not get a 500 error.
Fixed in latest. I went the easy route which is to stop throwing errors as it’s not simple to onebox playlists.