This is such a pet peeve of mine. Most of the time I have no idea what is meant by "initials." I didn't even know what the word acronym meant so had no clue where to look up the key. I proofread everything and circle the errors. It's a curse that I was taught in school, used in my work for 49 years, and never got over.
When I write something, I want the reader to understand what I mean. I always spell out words, even on texts. Rant over...