I don't think that is necessarily the case. If you use certain words all the time, shortening them makes sense. They might just forget which abbreviations are and aren't common knowledge. You wouldn't get mad if people use PC, CPU, ATM and RAM, right? Even SSD would be fine on HN, but it probably wouldn't be fine outside HN. (neither would using "HN")

I don't know why people can't take 0.3 seconds to type "what does CTA stand for?" into their favorite search engine/LLM/text-message-to-a-friend. This is "Hacker" News, yes? What do hackers know how to do? Learn things, yes?

Oh, and I also don't know why this needs to come up on approximately every single post that has an abbreviation that someone doesn't know.