I extend sincere compliments to everyone I meet.

Nice jacket evaporates on contact. It is pleasant, it is forgotten by the time the lift arrives, and everyone involved knows it was mostly a way of filling four seconds.

A compliment lands when it proves you were watching. That she rewrote the opening of the report three times and the third one worked. That he handled the furious caller without once raising his voice.

Sincere does not mean intense. It means specific enough that it could not have been said to anybody else in the building. People keep those for years, which is odd, given how cheap they are to produce.