Right, but the concept was created to talk about distributed systems and remote procedure calls where if a failure happened on your end and you didn't know if t

Right, but the concept was created to talk about distributed systems and remote procedure calls where if a failure happened on your end and you didn't know if the procedure call worked, you wouldn't have to check if it worked before retrying. So it doesn't quite fit here. Also, I don't think idempotence is a solution to this since a) This is more of a security issue, and less of a systems design one and b) you might actually have a legitimate use case for multiple posts