As a teacher I do it all the time with my students. It boosts their morale and motivates them!

This is a good question, because there are cultural differences between Russia and the U.S.

I think Americans have a reputation of complementing too often, maybe.

And perhaps Russians have a reputation for giving complements only when they are truly earned.

But maybe I am wrong, haha.

Treat people the way you want them to treat you. Words have great power. Compliments can motivate a person and help him understand how amazing he really is :)

Thank you very much, Armin!

To be honest, very rarely...which I recon it's a mistake as you should complement people as many times as you can, to make them feel important, to make them feel noticed