How do I pull up a users details on game?

[kiniki]

Got some guy constantly playing audio down the mic and want to know how to get his details so I can report him

 

[SogeKing]

Open up the console and type status.

 

[Existence.]

Not quite sure if this will work, but go into the console (press ~), and type status. Look to the right of the guy's name. If done correctly, it should show his steam ID.
Or just tell an admin.

 

[MorbidEwok]

Or if you know the name he was playing under check out the HLX Stats page (Player Stats link on the sidemenu) and search for his name in Team Fortess 2 and grab him SteamID from there.