That seems like a random rule. I've seen other forums incorporate the rule that it's "official" so long as it's the first thread on the topic. Seems to work just find so long as the mods are all on the same page in enforcing that rule and closing subsequent threads made on the same topic. I mean, the rule is already followed to some extent in practice. If I make a thread about aliens I want to see in S6 and then somebody the next day starts the exact same thread, theirs would be closed and mine would be left open for being first. I might not have an "official" branding next to the thread (which could always be added in at a later time), but it's still the de facto place to discuss that topic. I don't see what would stop the same principle from working in regards to episode discussion threads.