There are now several ways of inserting YouTube videos into comments (or into posts), but if you do it this way you can be certain that it will work properly. If you want to know more about the alternatives, try reading this WordPress article.
It’s really very easy. Here is what you type –
Please notice that the url must be a proper one, not a shortcut version which contains tu.be – ie. a full stop in between the “tu” and “be” of “tube. You can get the correct url from the address bar when you view the video on the Youtube site.
Notice that there are no spaces and that there is an equals sign between ‘youtube’ and the start of the url.
Further observe that there is only one ‘get’ parameter (stuff after the question mark). If there is an ampersand (‘&’) in the url (or more than one), remove it and all the text that comes after it. The url must finish after the “v=string representing the actual video“. In this case v=dFdas-kMF74
Don’t forget to start with a square bracket, and finish with one.