Dear Mary: I’m friends with a colleague twice my age, but I worry our banter and private messages are inappropriate

Question: A few months ago I started working in an office in the public sector. I am 19. At the same time other people were starting too, including a 40-year-old man. We get along like a house on fire. It is mostly childish stuff, basically memes or pop culture references. He is surprisingly aware of what’s going on in the celebrity world for a man of his age. Honestly, it’s ‘fart joke’ level stuff and we are both usually reduced to giggles by the end of coffee break, much to the confusion of our co-workers.