Why so deferential about posting write-ups? I'd just have a rule that says don't post write-ups and posting a write-up will get you banned from future editions or something.
Because in almost every other case that involves security challenges you are generally encouraged to post a writeup, and this one is different.
Because giving a good reason is usually enough for most people to follow something. Not everything has to be a stick (which you can wield anyway).