I have added a YouTube embedded video link capability to our forum.
There's a button at right above the message editing window to enter.
Use "youtube" inside square brackets, followed by the YouTube video number, followed by "/youtube" inside square brackets.
[ youtube]CODE[/youtube] (without the space after the first square bracket - I can't type the exact thing here because it gets processed as a video link and fails).
Replace the "CODE" with the YouTube video number.
e.g, for the video https://www.youtube.com/watch?v=BKPcWkIna9k just put the BKPcWkIna9k in place of "CODE". Just like this...
youtu.be/BKPcWkIna9k