The article's about oral vs. written linguistic evolution generally, but this bit makes me want to write a pseudo-scientific article about the evolution of Mythos cultist languages:
If such a language seems unlearnable, well, that is exactly the argument that linguists such as McWhorter have been making: that an adult venturing into Ket would inevitably mangle it, just as an adult learner of English may never quite grasp its irregular verbs or idiosyncratic prepositions (why do you say in a club but on a team?). The unpredictable aspects of language, the things you just have to know, may be especially slippery for the adult mind—and there are so many more of these in Ket than in English. This could be why languages that rely on dense words in all their irregular glory tend to be esoteric—that is, spoken within small and insular communities, where everyone who speaks the language has been marinating in it since birth. The inscrutability of such languages may have the effect of repelling outsiders, ultimately reinforcing their insularity.