@ms, no. I guess it could be made to do something like that though. It just puts a Gravatar in-front of the user name – meaning it only works when people use their email address as name. There is a long-standing issue over at Github about implementing hooks for saving extra user data (e.g. email addresses): https://github.com/Kroc/NoNonsenseForum/issues/156.
With time anything could be build ;-)
@Johann, that’s true. But I think the beauty of @Kroc’s idea is that it takes the ‘YouTube URL on its own line’. How often have you written an link with no punctuation or other text on an empty line when you only want to link it? Normally when the purpose is to give just a link this will be within text.