There is a guideline 1.2 that specifies what you need to do if your app has user generated content. Here they are:
- A method for filtering objectionable material from being posted to the app
- A mechanism to report offensive content and timely responses to concerns
- The ability to block abusive users from the service
- Published contact information so users can easily reach you
Have you implemented them?
Please share your experience in the telegramgroup Apple Review / app Submission / Approve / Reject / Appstore Connect/ Apple Developer / iOS - there are many guys who share different cases concerning apple revieew and so on