In chat, I wanted to post a link to a question, followed by a relevant YouTube video. Because I wasn’t paying attention, I posted the video first by mistake. No problem. I edited the existing comment to be the question instead, and then posted the video. Except that it wouldn’t post: nothing happened at all when I tried. I think it was the duplicate message filter preventing me from repeating myself, even though the previous message had been edited,
I posted a nonsense message, then the YouTube video, then deleted the nonsense. This worked, but should not have been necessary.