First of all, talk about the background.
Ghosts are a mark left by the dead. They can talk and think, but they can't enjoy food or grab anything. One day, they were tired of this kind of life, and they began to have the evil idea of possessing living things. ...
Not all ghosts are at Hogwarts, but there are many ghosts at Hogwarts. People with weak magic and willpower will be bewitched by ghosts, and then possessed by ghosts and become ghosts' puppets.
The consequences of being possessed are serious. Some ghosts have not simple motives. They either want to get rid of the demon sister, or they want to make the living surrender to the ghost.
The headmaster of Hogwarts has made full preparations for defense. The powerful and thoughtful headmaster made new rules and regulations and made all the preparations before the students returned to school. But the ghost focused all his attention on how to defeat the headmaster, and finally the headmaster was possessed.
So, draw the point. We already know that the headmaster was controlled by the ghost only after he wrote the additional school rules and rules to the teacher (not completely controlled, after all, the headmaster is very powerful, just a little conscious).
Then, "additional school rules" and "additional rules for teachers" are completely correct and trustworthy.
From the "Announcement", we can clearly see that although the contents of the announcement are very clear, there are contradictions with the "Additional School Rules". One is to walk together, and the other is to act alone and say, "don't tell anyone." Moreover, I don't know if you can see that the first three items of the announcement are to prevent students from contacting with the outside world. Owls, post offices, and going home are all banned.
The first announcement is unsigned, but we can know who may have written it through announcement 2.
Announcement 2 is very strange. The signatures are all from the headmaster, but this announcement is "messy", with confusing words and many spelling mistakes. In fact, the announcement 2 was written by the headmaster of Hogwarts when he was possessed, and it was very tangled when he wrote it.
Announcement 2 mentions that only the headmaster, the administrator and the president of the boys' student union can be trusted, but the person who wrote this announcement cannot be trusted. So these three trustworthy people can't trust, that is, they are possessed. The person who wrote the first announcement should be the squib written by Filch. Because it is a squib and old age, it is completely possessed, there will be no struggle, and the word order will not be chaotic, which is very clear.
Then there are two very important points, possession and "treatment".
As can be seen from the original work, Ginny was possessed by Riddle. She also said that the feeling of being possessed was that "there was a big gap in memory and I didn't know what to do", so the principal who was not possessed asked the students in this situation to seek the help of the teacher and "receive treatment" in the attached school rules.
According to the additional rules of teachers, the so-called treatment is "treatment", and treatment is probably killing students. This is to prevent the possessed students from continuing to be controlled, which is a necessary sacrifice to stop the ghost plot.
Finally, it is an explanation.
As mentioned above, three people you can trust cannot be trusted, including the president of the boy student union. It is unwise for a Ravenclaw to sneak into the library at night and study all night, but it is also reasonable. He acted alone and was vulnerable to attack, so he was possessed in the library. This note was a clue left by his struggle when he was possessed, but it was destroyed.
It is not difficult to see that the original text is:
I am the president of Ravenclaw Boys' Student Union. Help!
Ghosts are not to be trusted! ! ! They tried to attack me!
Don't come out alone at night! ! I'm under control!
Help!
This is the end of the analysis. I wonder how much you guessed right.