That’s a good observation. I think it’s where their heads are facing. Two conversationalists face each other or face the room, but talk quietly with body language that suggests they’re conversing (heads tilted, leaning.)

Someone talking on the phone but facing away from the room isn’t usually considered rude, either.

In a waiting room or train car, if you’re sitting and talking on the phone or Zoom, you’re broadcasting into the room with your posture. Your voice tends to broadcast as well with no wall or other conversant as an immediate barrier.

I would consider two people talking to each other in a waiting room or on a train very rude too. If they are loud enough that the people next to them or behind them can hear the words they are saying, then it is rude of them. Of course, this is relative to how noisy the place is overall.

These kind of social rules are why I’m very glad that America has garbage public transit culture. Actually I am going to jabber on talking to folks during transportation events. I’m going to do it in my personal vehicle so I don’t have to deal with others crying about my behavior.

Only poor people are required to humiliate themselves by asking every tom, dick, and harry for their opinion on if their behavior is acceptable.

The number of people blasting video on a regional flight with no internet really made me reconsider just how necessary airplane mode is. Probably an applicable case study for many other societal boundary-breaches silently spreading.

I don't mind people having conversations, just don't blast the volume up or put it on speaker for the whole train to hear..

Having lived in both Australia and Japan and visited SK, for me it seems like it’s rude in all those places but only in some places do almost all the people care what strangers think enough to modify their behaviour. Which is not as judgmental a statement as it sounds like, because that care, or some might call it pressure to conform, has upsides and downsides.

UK, unless you are quiet about it. Though you might not notice as our reaction only tends to be in body language, or for particularly loud speakers (particularly those who are GOING INTO A TUNNEL or otherwise think shouting will help with bad reception) we might tut.

It's considered rude in Belgium, at least when I commuted there by train. People would leave the wagon to take a call. Maybe it's changed in the past few years. There were also signs that it's prohibited to call in the trains.

i’m in the US, if you took a call for more than a few mins a busy metro car I’d tell you to knock it off