What is stored, and where it goes
What is stored. Your nickname, the name you asked to be called, an email address if one was given, a hashed password, your route answers, lesson progress, trainer runs, journal notes, review cards, review threads, the agents you build, the images you generate and any certificate you earned. Nothing else. Your name is the only one of these that a stranger can see, and only on a certificate you chose to hand them.
A request for access. If you left one on the main page: the address, the name, the answers about your routine and the note, until the account is set up or the request is declined.
The model. Trainer runs, the Mentor and the judge send the lesson text and your own messages to the model through the course account. They are not used to train anything.
Images. What you write in the Lab goes to the image service through the course account; the results are stored as your assets.
What the teacher can see. The teacher sees your progress, your runs and what you send for review, and nothing you did not save.
Deleting. Export my work gives you everything as one file. Delete my data removes your account and every row that belongs to it, at once, with no copy kept.