A trainee recently gave me a link to an interesting exchange between a Chinese pilot and a controller at JFK. The pilot could not manage a simple taxi and hold readback, so I guess we were all supposed to laugh at his embarrassing lack of English. But the controller's strategy was to raise his voice and become agitated. I imagined the capt and copi cringing on the flightdeck. That was not going to help their situational awareness!
Any speaker may be over-fluent, too elaborate in structure and vocabulary, or just plain inconsiderate in interactions
I am English and native English speaker and I occasionally have difficulty with American controllers. They often speak very fast and use a lot of non-standard phraseology.