I have got into the habit of having my child pass messages to my ex-spouse. Why is this harmful?

Making your child the messenger puts them in the middle of an adult conflict and forces them to choose between two people they love. It also opens the way to misunderstandings and makes the child feel responsible for the tension between the two of you. Communicate directly with your ex-spouse about the children, through short polite messages or one agreed channel. Keep the conversation to the children only, not old issues between the two of you. If direct communication is too heated, use written notes or a trusted go-between. Let your child just be a child, not a postman or a spy. See communication & emotions.