I’m not sure of the reason for a warm tongue but I have heard that a way to tell how hot/cold a bunny is would be by feeling their ears. Someone can probably expand on my very short answer haha. Sounds like your bunny likes being brushed, your very lucky to be getting licks

Buns often reciprocate by licking your hands or clothes when you groom them. It means you’re great friends. Buns’ tongues are always warm in my experience.

There are times Wick grooms me and his tongue is so hot I’m like, okay stop. It seems like a normal fluctuation to me.

Dasherbun, there is a specific meaning: It’s about maintenance and reinforcement of the bond between, in your case, your wife and the bun. When buns live together they spend a lot of time grooming each other. In some pairs only one bun gets groomed (the top bunny), in other pairs the buns take turns. It’s very important for rabbits. Horses do much the same thing, they can also form a strong bond with another horse.

But it’s absolutely not a sign of a health problem. Quite the opposite, it’s a very good thing.