To insert a YouTube video into a comment:

Copy the YouTube URL and paste into the comment.

Insert a v into the URL, right after the p and before the : [colon]

e.g., if the URL of the video is

http://www.youtube.com/watch?v=oOGs8TtnwoI

then add the “v” so it reads

httpv://www.youtube.com/watch?v=oOGs8TtnwoI