The phrase often suggests a discreet disclosure, not always direct or obvious.

Subtlety Matters

Showing inadvertent signs of feelings, despite trying to conceal them.

Emotional Nuance

Sometimes people let on information by accident in a conversation.

Often used to express pretending not to care about something.

Sometimes used in a sarcastic or ironic manner to highlight contrast.

Can sarcastically indicate that you pretend to believe something unlikely.