Try something like emailing the link to yourself first and copy and paste the link from your email to the thread. This may work. It's worth a try. Good luck
Below are both using awndray's technique, neither of which work as advertised.
(which you can verify if you use a "reply with quote" to see exactly what I've put here. Neither of which are what I want, namely link only.)
I note that awndray's technique works on every other bbcode compatible forum I've used for years.
Namely
[ url = ht tps : / / w ww . youtube . com / watch ? v = sFMUeUErYVg ] test [ / url ]
[ url ] ht tps : / / w ww . youtube . com / watch ? v = sFMUeUErYVg [ / url ]