Does this turn you into a sycophant? No. There’s a difference between sucking up and giving legitimate praise. You’re not making blanket endorsements of their conduct, only singling out specific instances of good behavior. Constant flattery is a no-no; it only feeds unhealthy narcissism. If you have nothing nice to say to a highly narcissistic boss, don’t say anything at all. But if you see an action you like, make sure you point it out, clearly and sincerely (or you may never see it again).