It’s not a HIPPA violation. That law doesn’t apply to companies like Meta beacause they do not fit the definition of an entity that the law was written towards. This is just people freely giving away their personal health information and nothing more. From your own link:
The HIPAA Privacy Rule establishes national standards to protect individuals' medical records and other individually identifiable health information (collectively defined as “protected health information”) and applies to health plans, health care clearinghouses, and those health care providers that conduct certain health care transactions electronically.