Hoffman was a founder of Reddit, he was a part of the very creation of the site. He also had absolute and unlimited access to every bit of data that reddit ever had or created. He was also well known for editing other people’s comments for his own amusement and narcissism. He not only could have easily been the creator, but he could have been the very mod who made his other account “a mod as a joke”. He definitely could have removed himself as a mod of jb just as easily as any of the other well known edits he did to Reddit. And he definitely had direct and unfettered access to every single photo that was ever uploaded or linked to Reddit, even the ones that were so illegal that even the jailbait mods took them down.
So, the other guys opinion that Hoffman was the head pedo and creator of jailbait is just as valid and verifiable as your opinion that it was a joke that he nothing to do with it.