Have you read my post?
However, there was a thread in a certain subreddit that advise people to stay completely still when they see a mentally ill man displaying erratic behavior. From experience, some mentally ill person will not just be screaming, but run back and forth the train.
Even if that is the case, many users still recommend staying completely still and ignoring them. Their take was that if someone get up to leave, it will catch the mentally ill person's attention and spark a conflict.
To me, it sounded absurd because people should be able to leave an uncomfortable situation without being attack. I find that these mentally ill homeless people tend to like feeling powerful are are empowered when they see nothing will happen to them when they yell and scream at people.