What if a guy is taken but still flirts?

this one guy and I met and connected instantly. We talk all the time and we've confided to each other. He is taken but told Me he isn't hopeful for the relationship. He seems to flirt. Trying to make me laugh and smile(I do the same) touches me on the shoulder or brushes against me, always stares at me and smiles at me and tries to talk to me all the time. What does this mean? What should I do?
What if a guy is taken but still flirts?
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