... so NC/NCO can not be added to the CFPA I18nUpdateMod repository (the largest translation provider in China Mainland; there is another one in Taiwan called RPMTW which provides Traditional Chinese translations and uses the same workflow as CFPA; I will describe the mechanics later) and the translations is not automatically updatable via IUM or RPMTW.
We can add prefixes to some NC/NCO keys to solve this problem (certainly with corresponding changes in the code), but to guarantee that in future there will not be more key being shared, I think we should add a prefix or a "mid-fix" to every NCO key (maybe in this way we might only need to change the whole translating function for NCO and this would be easier? I am not sure).

How IUM works:
The translators put translations to a folder (structure: curseforge-domain\mod_id\lang\en_us.lang & zh_cn.lang) on GitHub so the repository stores every key of every mod submitted; Github Actions packs the language files as a resourcepack when a commit is committed; IUM on Minecraft client download the latest pack when the game starts and install it automatically.

Now as one is not able to know what the player installs (NC or NCO; actually it is possible to know that, but it would be too difficult to make two packs for NC and NCO and let the client check which one is installed and download the correct pack, the packing time of GitHub Actions would also increase and that might lead to the need of more time and GitHub PRO), he can not simply put all the keys into IUM repository because same keys of both NC and NCO may not have same key values in English, therefore the key values in Chinese are not the same, if they are shown to the players in game, the players will get confused.

This is not an important issue, because this is more an inner problem of the mechanics we are using rather than a problem the modders need to solve, so please excuse me if this bothers anyone.

It has been long that I did not speak English frequently, so if there is mistake or unclear description, please tell me, I will fix them.