If it is a recorded research article presented at a conference, then search for the conference and get the info u require. But if its just a channel with no ethics, then it's difficult to reference that. Expect during an oral conversation.

There is no confidentiality issue, since the Youtube commenters have put their comments in the public domain. Confidentiality in social media could only become an issue if the content was made available just to a select group of which you happen to be a member (e.g. "friends") or else you have somehow managed to bypass a poster's privacy settings.

Nuno Piçarra, The whole point of using data from social media (comments) is the fact that it has been shared by the user willingly. More often it provides more valuable information suitable for sentiment analysis! Information from twitter, Facebook have been extracted by many researchers for data mining !