I would say, given the subject of the thread, it was still "on topic", and the thread hadn't become abusive or argumentative in any way.... if we get consensus on the charter, I would follow the "light touch" principle and leave this one open. However, I am not going to second guess anyone until that charter has been approved! I think Andrew's comment about being consistent with each other and the principles of the charter are critical here. Although the thread might not have been terribly useful, it isn't for the moderators to kill off discussion in subjective calls unless one of the principles has been breached.
There, I've had my say