I've been given a spoiler warning/edit erroneously before too; the people handling that are regular folks, they can make mistakes. I simply sent a private message to the one who edited, had a short civil conversation with them explaining why my post wasn't actually a spoiler, and they went ahead and edited it back to normal. They kind of probably have to take any reported spoilers at face value a lot of the time, it's not like each mod has read every chapter of every series on this site and all. Bound to be some spoilers that slip through the cracks or some non-spoilers that get hit.