My question might sound silly, but I plead ignorance. I am studying Serbo-Croatian or BCS or whatever you might call it. I just wonder how ex-yugos can distinguish who's who - let's say, on street. You look the same. The dialects overlap state borders (I learn in parallel Serbian and Croatian, no need to explain me about ekavian jekavian etc). So I wonder how even, during the 90's yugoslavian wars, one could be identified on street as Serbian or Croatian or Bosniak. Also today, I hear from time to time in the news that said Serbian was discriminated in idk which Croatian shop because Serbian. How did they knew it?? I have only notions of Serbo-Croatian and can easily fake both accents and use Serbian words or Croatian words to make the difference.

Tld;r: how the hell is a Serbian identified as Serbian in Croatia, a Croat as Croat in Serbia and so on.

I have Serbian friends in Kragujevac and while being with them they met a friend on street. With my miserable Serbian notions I said a few phrases and he asked if I am Slovenian, lol.