I tend to mostly trade with friends, esp as I hermit and they come to me but I have also traded with a few now from the established traders and never had a problem of any kind. It was just unfortunate that there were a couple close together and also Petal wasn't an oath killer, she was just involved in the argument.
I have to say though that I almost traded with Holya, he had something I wanted and he seemed nice but as he was unknown to me I was just a little bit cautious and luckily he messed up before I decided to go ahead and risk it.

And not all Polish are bad Jordan, lol, my neighbours were a Polish group and they gave me perms in their village, access all areas, to take whatever I wanted, when I needed it, this included higher metals than I was producing at the time and higher wood products. When they moved in with another group they then gave me the keys to the village - and all of that was just because when they started I let them mine some of my ore, a tiny little bit in comparison. These Poles were wonderful!

So, it also pays to be a good neighbour and get to know your neighbours, most of my area have quit now but at one time it was lovely, we all shared all resources, one had good q water, another clay, I was ahead in crafting and survival so I made everyones tools etc, it was sorta like one big village all spread out, it was fun.