Ha, I was just called "gui zi" the other day. I was sure it was something nasty. 99% of the time I'm called "Lao Wai" or "Wai guo ren" or "Mei guo ren" or even "Ying guo ren". Bit of a pisser being called a devil. 'Course I definitely do live in the "backwater" type of town, and possible the spitting epicenter of the known universe.

Related, often the greetings mentioned in other posts recently are NOT friendly, but deliberately mocking. For example, "Hello wai guo ren" (hello foreigner), followed by laughter. One could chalk this up to nervous laughter, but I've heard, "hello f_ck your mother" too many times now, and can't possibly not see that as rude. If there is that extreme, there's every shade in between.

What clued me to the "gui zi" being pejorative was the way it was said, even though I didn't know what it meant. So one can tell a lot from delivery. There are people who say hello to one's face, in a kind way, and those that shout it at your back after you've passed by and then laugh in groups. The latter are being asses.

Unless Chinese people are the most polite people in the world, their behavior is nuanced, and they are NOT above poking fun at the defenseless foreigner who can't speak Chinese. Though if you can it will embarrass them to be found out talking shite about you.

The downside of your informative post if that now I know what "gui zi" means, and I'm likely to hear it a lot more. My first blissful month in China (actually a nightmare because of the corruption of the institution I worked for) I didn't know the words for foreigner. After I learned them I realized people talk about me all the time and everywhere. Not a terrible thing unless, as can happen sometimes, one isn't in the best of moods. No one needs people pointing at one while one's blowing one's nose, for example.

cheers