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

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.