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> This can be used to create profiles about personal preferences

And since it's not, so what?

> I might be processing personal health data identifiable as such in a private repository with the help of Copilot.

That remains nonsense. The fact that you could put PD in a place not intended to hold PD does not magically transform entire datasets into PD because 1 record may contain it. This is covered in a24 (risk-based), and multiple edpb discussions of proportionate measures. There is zero requirement to guarantee anything collected for a different purpose is not misused by the user, assuming you're not encouraging that misuse.