What kind of vulnerabilities might exist that allow randoms to get your IRL name?

In a lobby just now with randoms that queued together (both making jokes and riffing with one another) and eventually after they both died, one started calling my name curiously (as if to test if it really was my name) and repeatedly called it out (with a questioning tone) before leaving?

I can only assume he got it from my windows username, which is my IRL name? It's not exactly the most threatening gesture but it definitely piqued my interest. It's not the most common male name, otherwise I might assume it's just coincidence, but he seemed determined to elicit a response from me by calling my name out like 8 times. How does one obtain that just from being in a lobby with me? Anyone experienced this?