Your reaction is information. Give it away for free and people learn exactly which buttons work.

Reactions teach people how to operate you. If one particular comment always produces a flash of anger, that comment becomes a tool, and anybody wanting a response will reach for it again. None of this requires cruelty, only noticing, and most people notice without meaning to. A level face is not fake, it just keeps the information to itself.

Work out which two things reliably get you. Then practise the gap: breathe, say nothing for a second, answer flatly. You are not pretending to be unbothered, you are choosing when to show it and to whom.