Links and whatnot are fine if they’re actually relevant to the discussion - just not great to have spam links to random websites when there’s no reason for them 
If you paste a youtube link on its own line it’ll get embedded in the forum post though (as covered in the How to Use the Blue Robotics Forums guide), which can be a bit more readily accessible than having to go to a separate website, especially if there’s something in particular you want to highlight.