Now I remember something. Some months ago I was using those YouTube codes, the ones that are shorter and in bold print. Then all of a sudden doing that did not work. I took the question to the Support Forum and you told me that we had to use the URL at the top of the page in the Address field because the short codes did not work any more.
At that point, whether I was copying and pasting the short code or not, I was following the procedure taught by WordPress: Click the video media button, then click "By URL" and then paste in the YouTube URL.
If this procedure has changed and been announced, then I have not read it or found it.
However: If putting the brackets around the short code without clicking the link button will assure that an actual picture of the YouTube video shows up, then I will do it. In the past, when I just (accidentally, due to bad memory) typed the URL in the text field, then that showed up, but it was not nearly as attractive as seeing the YouTube video with the picture in it.
I will go and check it out now and see if it works. I will revert to using the YouTube short code and paste it in, surrounding it with brackets, which I guess fools the system into thinking it has to show the YouTube picture box.
(I think maybe I got one extra silver hair out of this. :-) :-) :-) :-) )