It's like writing "pusillanimous" when you want to say "nice" -- the chosen word is both unnecessarily fancy and wrong. I'm not aware that this has become the c

It's like writing "pusillanimous" when you want to say "nice" -- the chosen word is both unnecessarily fancy and wrong. I'm not aware that this has become the conventional understanding just because some people here and there make this mistake. It's fine for words to acquire new meaning, sometimes even an opposite one like in the case of "literally," but even in that case the word serves some purpose (that of emphasis). So if you tell me that the word "formal" has acquired the meaning informal, I would still ask what purpose does "formal" serve here? What's wrong with just saying proof? And yes, I did need to scroll to the section about the proof to see that the article does not, in fact, provide a formal proof. I agree that this is pedantry, but in this case the article emphasizes formalization so much that it seems like it's a central point, and yet no formalization is to be found. To me this suggests that some people may simply not know what "formal" means in this context, which is fine, but since this is an important concept in computer science, I thought it is worth pointing out.