Worked at a Chinese company in Shanghai before. Everyone on my team could read/write but not speak English. It is most common that people would write code in English but use Chinese for comments and documentation (both internal and external). We all used Sogou which makes it easy to make a hotkey to easily change between Chinese pinyin input and English.

I am lead to believe this usage of English for code and Chinese for comments is quite common given the code I've read from public repositories and other companies we worked with.