Writing letters of reference for a faculty position in China?
Writing my comment as an answer, following a suggestion.
I’ve spent two years in China as a postdoc. I have never read a recommendation letter (LoR) but I’ve experienced the culture in academia. As someone else hinted I also do not think anybody will actually read the LoR in any detail, but just skim through it. The focus is on who wrote it (more precisely, what is the author's university ranking and impact factors). About the contents I’d recommend just dropping cliche positive comments but without any exaggeration. The Chinese are extremely sensitive to any form of criticism, and will generally not appreciate outspoken, frank discussions. This will look particularly "serious" if put in written, from a "leader" and addressed to 3rd parties, and might be interpreted as a gentle warning against the candidate.
Do not write about weaknesses in a reference letter for China. Your candor and frankness will not be appreciated as a dialogue...or friendly critique.
My recommendations:
Highlight the applicant's ability to publish, particularly if they have a large number of publications, and particularly if they have publications in journals with a high SCI ranking (SCI 1 or SCI 2 journals, especially; searchable from LetPub). There's other ranking systems, e.g., in computer science, we also use the CCF index.
Highlight international collaborations that the applicant is able to bring to the university.
In my opinion, the above two items are far more important than anything else. These are always the top priorities when we have meetings---who's lab published what, and with whom.
If relevant, highlight the applicant's English level, especially if they're a native English speaker. If possible, highlight the applicant's willingness to improve the English on student papers.
If relevant, name the professor(s) the applicant is intending to work with. In interviews I've been to, if the applicant can't name the professor, they're not taken seriously.
Highlight how the applicant has the ability to apply for grants reserved for international applications, such as the Research Fund for International Young Scientists.
Describe the ranking of the university where they obtained their PhD.
Explain how the applicant is able to adapt to life in China, e.g., highlight their Chinese-language ability, Chinese co-authors, and experiences travelling to China or living abroad. Make the applicant seem less "foreign", a friend of China, and unlikely to stir up trouble.
(Although if they're from China, Singapore, etc. [anywhere where they speak Chinese and the culture is similar to China], I'd skip this---they might not seem international enough.)
If relevant, highlight how the applicant is from a "Silk Road" country (interpreted broadly), which is in line with the government's Belt and Road Initiative.
And, I concur, don't write about weaknesses---they'll almost certainly be interpreted unfavorably.