Since no-one else mentioned it yet in this subthread, the phenomenon you are discussing is called a sociolect:

https://en.wikipedia.org/wiki/Sociolect

Basically, since class is culture, and cultures have language, a sociolect describes the language of a class, the ways you have to talk to perform that class.

And, naturally, this goes both ways. Someone talking the sociolect of a certain class is seen as performing that class, and therefore belonging to the class.

It should also be noted that the original article is itself a class performance! The author uses more complex words and grammar than necessary, thereby signalling academia or professional class. (Someone in the comments on that page wondered why this article had a more complex language compared to other articles by the same author, but didn't connect the dots...)