While I think your response was helpful, as many people don’t know that API calls are not used to train models. I don’t think it quite answered OP’s question. They asked if the data was kept private. To me that means, “Can anyone look at it? What are the risks of someone abusing that information?” Without further information, I would assume people bare minimum, who are on the moderation team could view and possibly even copy any data sent to the API, yes?
Also, here is the relevant privacy policy for the API. The one above does not mention anything about the API policy. API data privacy
Here is the most relevant text I found from that link.
“Authorized OpenAI employees whose roles involve developing, delivering, and protecting our API services, as well as specialized third-party contractors that are subject to confidentiality and security obligations, can access this data solely for potential abuse investigations, if you reach out to us with questions, or to comply with legal obligations.”