> Feeding someone else data into your system is usually a violation of copyright

In some circumstances, yes, but often it's not, especially if you're not continuing to store and use it (which OpenAI isn't).

I'm regularly feeding other people's data into my "system" (brain) in order to produce my outputs.

So I'm a living breathing copyright violator. As a person I should be banned.

Fortunately, copyright is a bullshit fictitious right with no basis in natural law. So I don't lose much sleep over it.

Computers are deterministic. Giving the same inputs training would produce the same model. The comparison with brain is incorrect. You could add noise on input data during the training - it would more of less reproduce the real learning. Still, it could produce less useable models as a result.

The court could ask to show the training dataset.