>>5889 (OP)
Rule cucking provides filtering. Imageboards are places where mass formations occur and they can be catalyzed or inhibited by the actions of a subset of participants. Rule cucking, if done correctly, may yield more effective board action by dampening disruption operations. It's what made 8chan's /pol/ actually effective compared to the shitfest at 4chan.
I think a good way would be to have a box where anon puts his "password" (say the field takes up to 1KiB) and that associates his posts on the backend, then webmaster can grant visibility of secret boards if he likes the post history (and revoke if poster can't follow the rules).