I have seen couple to threads where thread creator put a P.S type sentence where they ask some users not to reply on that thread & they point that as local rule of that thread.
Is rule like that really existed? Did any forum admin/moderator ever say user can have local rule on their thread? There's an option for moderating our own thread; self moderated thread.
There's no way for a user to apply personal rules on his threads. There's no moderation tools for users to excert their own authority over others on the forum, except of the report button maybe when global rules are broken. However, there's also the option to start threads as self moderated and in doing that, the OP can delete responses on command.