Where in the world did you get that idea? Blatantly wrong. If something isn't allowed, only the person trying to do that thing gets a message like that, no one else. I get a message like that often with some of the crazy stuff I try but you don't see it. But you can believe it works that way if you want. Just know it's not the way the software works. Now you might see a "not allowed" message if a moderator has put an image in moderation. But the software doesn't magically do it. It has to be executed by a person.And , the "No code has to be inserted here. " is something this sites software inserts when 'something' isn't allowed .
Actually that has much less information than than just editing his post to see what he was trying to do. Nothing there that would generate that message though. At least not that I can tell. We’ll see what the big guns have to say once they wake up and get to work. 🙄If you go to Logs > User Change Log in the admincp it may show what happened.