As a general rule of thumb, if I know someone's irl name in game, I always use their in-game name. Unless I am talking to someone who already knows this person irl anyway, and I wouldn't say it in a public chat. (For example, my FC is group of friends who know each other's irl names, have known each other for years, so sometimes a person's first name would be mentioned).

Otherwise, it's a bit of a d*ck move to mention people's irl names to a bunch of randoms.
A potentially dangerous move, also.