"Apps with user-generated content or social networking services must include the ability to block abusive users from the service." https://developer.apple.com/app-store/review/guidelines/

App Store Review Guidelines - Apple Developer

The App Store Review Guidelines provide guidance and examples across a range of development topics, including user interface design, functionality, content, and the use of specific technologies. These...

Does that apply to the other users having access to the feature, or is it fine for the owner of the service to be able to block users from the service? The way that's written, it doesn't seem like a user block is intended because a user block doesn't block a person from the service.