We need to add flagging rules to the FAQ but off the top of my head, these are the valid reasons to flag:

  • spam
  • scam
  • racism/bigotry
  • threats of violence
  • excessive and unnecessary meanness
  • unwelcome nudity
  • encouraging self-harm

A lot of these are subjective, which is why it's optional to see the consequence of flagging.

There is no "policy." Just suggestions, votes, payments, and algorithms.