I must say Definition 1 of 1Pro Tip 1/3Subtle Agreement Use when you agree but want to acknowledge others might not feel the same way. I must say, your idea does have some merit. Pro Tip 2/3Polite Contradiction It softens the impact when you are about to contradict someone or something. I must say, I see things quite differently. Pro Tip 3/3Mild Surprise Use it to express a gentle or polite surprise about a situation or fact. I must say, I didn't expect such a warm welcome.