For me, it goes back to the type of gardener one is or perceived to be. If one of my friends, who I knew to be a casual gardener, said look at my Christmas cactus!, I would probably admire it and move on. On the other hand, if a friend who I knew was very interested in her plants said that, I might tell her all about the different 'Holiday' cactuses.
My guess is that most people posting here have an interest in gardening and wouldn't take offense at being given information about the plants they grow.
