What does “trade” in the text of the “Diplomat” mean and do trade-in effects come into effect?
You can treat it like a normal trade. So the “Diplomat” must give some card in exchange. Trade-in effects also come into effect in the order of a normal trade: First for the “Diplomat”-Player, second for the other player of the trade. Notice: You may use the privileg of the “Diplomat” additionally to your normal turn.