It is what it is. Person 1 will post a seemingly normal one-sentence story, Person 2 will post a humorous, shocking, or terrifying plot twist of Person 1's message.
example
Person 1: Henry treats his girlfriend like a princess.
Person 2: ..so he married her off to Poland to strengthen their political bonds.
I apologize for any reposts I looked up "lot twist" on the forums but nothing came up.
as his therapist looked down on, depressed, and desperate. All of therapy so far has failed, and there's nothing they can do. The kid spends rest of his life at a madhouse.