This:
26.
Those were mostly replaced by self-moderated topics, but local rules can be enforced at the moderator's discretion.
It's something I've seen around the forum. OP can't create a Self-moderated thread in the Meta board, so I understand why he chose to add a "Local rule" but again...
If you don't want other forum members responding to the thread then you should have sent them individual PMs, PASS