assume that the third person is actually listening to the conversation

when you are with a second person talking about a third person, you should assume that the third person is actually standing there listening to you talking about them. often we assume that the conversations are private, but that might not be the case always. the third person might be actually listening to the conversation from somewhere and you might not be aware of it (a setup by the second person).

what if the second person decides to share what you said about the third person, in a gossip of some sort? the president of united states did that, so it's not unreasonable to think 'anyone can do that'. it's better to talk nice but if you are pissed off because of something the third person did, just know that whatever you say won't remain private even if it was said in a private setting.