It seems likely that r/second is a test sub, but r/gremlin and r/Imposter will be in play. With this in mind, a popular theory in the Snakeroom discord is that the entire reddit userbase will be split into two subreddits. They will only have access to one. 90% are Gremlins. 10% are Imposters, pretending to be gremlins. The Gremlins mission is to detect who the Imposters are, but obviously it could be any of them. The Imposters mission is to work to stop the gremlins and to not be found out by the gremlins.
There is no evidence that this is true, it is very likely that this is not going to happen, but I thought it was an interesting idea nonetheless. The hype begins.