This little rant is about naming articles and categories, of mainland China.
Mainland China is an interesting term of art. It is defined not by what it includes, but by what it excludes. It's a term created by and defined by those who are excluded. It's not alone in that; witness: Metropolitan France, English Canada, Mainland Finland, etc (there is a whole list of these at Mainland). Prior to 1997, it included all of the territory of the People's Republic of China (except Taiwan). The term "mainland" was coined by the Kuomintang, who needed a term to define that other place that they claimed as theirs. After 1997 it became an increasingly useful term for those in Hong Kong as well.
What makes it interesting on Wikipedia is that the majority of Chinese editors are not from the mainland at all, and for political reasons probably resent the PRC government. Even though it is the most populated nation on the planet, the PRC censors Wikipedia making it too difficult and inconvenient for their residents to maintain accounts (and probably a crime if they admitted to it). It has no native representation on Wikipedia. For anyone from Hong Kong or Taiwan, it is an entirely natural term, regardless of politics. The mainland is that place over there. The PRC makes it difficult to enter or leave, so the mainland, in thought, is just one big monolithic entity that can be safely ignored in everyday life.
So for these editors, it is natural to use this monolithic term to organize and describe things on Wikipedia. That is where the problem starts - mainland China is not a monolith. And this term, created and defined by those excluded from it, is being used as "us and them". In that paradigm "us" is wherever they are familiar with, HK/TW, and them is the nebulously named "mainland China".
In the case of Taiwan, it's an easy enough split because of the reality situation on the ground. The PRC claims Taiwan, but doesn't govern it - it is easy to call those things "PRC". For Taiwan, those things are easy to call "Taiwan" or "ROC" without ever using "mainland" at all.
"But Subject X doesn't apply to Hong Kong!" For Hong Kong and Macau, it is different because they are part of the PRC. From that perspective: PRC - HK = Mainland. Easy? No way! Because what then is the totality of things belonging to the PRC? Zero! So all subject matters of China become "of mainland China" because of the existence of Hong Kong? I don't think so.
This also creates a hierarchy that says there are three divisions of the PRC. Hong Kong, Macau, Mainland. Is that the case? No. Hong Kong is just one of 33 administrative divisions. It's not more important, it's not less important, it just has special rules.
unfinished.