I've been watching Fantasy High, the series of 5e sessions filmed and posted on YouTube by alums of the website collegehumor.com. At a certain point, the DM has an NPC do something that uses a spell mechanic I can't identify. Would it be appropriate to post a question on main asking for help identifying it, along with a link to the video and an exact time stamp?
That seems like a perfectly reasonable content-identification question. Linking to the source material is great, the only addition we'd want to see is that you also include a description in text in case the video goes away (we want the question to still be understandable in such a case) and for the benefit of those who can't watch the video.