This is more than just feeling pleased. There is the effort to show appreciation. There is the effort to make other people feel proud of their achievement. Expressing appreciation is often difficult because anything that is said always seems to be inadequate. Emotional and outgoing people may manage it better. For other people flowery language and behaviour seems insincere and excessive. Code 10/20 provides a clear means of signalling appreciation. Some people are better at delivering compliments than others. Some people are better at receiving compliments than others. Code 10/20 could be used to deliver a compliment and code 10/21 to receive a compliment.