I say something nice to/about my T in probably 70-80% of our sessions. Usually it's something like, "That's a really good idea," or, "That's a much more diplomatic way of putting it--thanks." Sometimes it's more detailed or personal, like, "I appreciate your patience," or, "X was an excellent intervention." He's never seemed to preen under it in any way that freaks me out or makes me feel obligated to make him feel better. Certainly he doesn't seem needy for compliments or reassurance--I would not see a therapist like that--but who knows? Maybe he's just good at hiding it.