A compliment may not heard or even used against you when given to certain individuals. These individuals have the ability to twist such positive words so they appear to be even an insult. Sometimes even a person who appears open to hearing such positive words is not in the mood to listen or is so absorbed in another thought so that your words will be absorbed from the wrong body part.
It’s worth testing the water with a light comment to see if your compliment will fall on the wrong individual or at the wrong time before you express your full gratitude. Maybe a slight positive comment about their appearance or the direction of the day and their response will determine your next move. Seeing you positive comments turn to closed ears or being misinterpreted can turn any frown upside down. Therefore the question might be not just to compliment but to whom and is so when?