Record with 2 microphones without hearing yourself twice?

Twitch or anywhere else, you can often see them recording together in one room. So both have their own microphone and sit opposite. How can it be that you don't hear both through a microphone? So e.g. Person A records with micro A and person B with micro B. How can it be that person B is only heard through micro B and not through micro A? If that's an attitude, how do you adjust it? Lg

Important, very well insulated room! Little reflections! Directional microphones, of course. Best dynamic mics. That's it.

There's always talk, but the volume can be greatly reduced.

Great answer