Lauda, suchmoon, I agree with both of you. And you are right, forcing someone to read something will most of the times create the opposite effect. It is like the terms and conditions that need be accepted before installing a new software.
But if it is done properly, highlighting that they WILL be banned if they plagiarise, and what to do to prevent being banned, it might get some of them to read it.
Actually, the moderators do have some latitude on exactly what action to take on a post that breaks the rules. This can be anything from deleting a post to an autoban. (or no action at all.) I have seen cases where a member is not autobanned for a copy paste. They usually take into consideration how old the post happens to be, if it can be contributed to an error, and whether it appears to be financially motivated. Also, the rules are titled "unofficial." From what I gather, Theymos is not interested in micromanaging the moderation of this board. He has delegated this responsibility to several moderators and mostly leaves it up to them to make fair decisions. He will step in if someone has a complaint about the moderation that seems to have some merit and that he disagrees with.