Гарри Поттер и тайная комната

The way the diary acts as both a plot device and a character makes me wonder what inspired its dual role in the story. Did she plan this from the start or develop it during writing?

The rivalry and suspicion at Hogwarts seemed to escalate here, making the school feel more dangerous. Was this a deliberate choice to heighten the stakes?

The hints about the founders and the past add layers to the mystery. I wonder if this storytelling approach was planned from the beginning or evolved as the series progressed.