> I'm from a lower class background; I learned from early on to adapt my language to that of the upper/upper-middle class
I have a similar background, but I can't say I adapt my language to that of upper classes. My accent and skin color pretty much gives away my background when I utter my first word, and unfortunately, just like having a southern US accent, people are subconsciously biased to thinking I'm probably not too smart. I love using "ten-dollar words"[1] - not that I shoe-horn them in, but they are the ones that usually pop into my head first and I can't be bothered to water them down. Additionally, I figure, "dumb" accent + "smart" words cancel each other out - more or less - which puts me on equal footing with my "normal" sounding colleagues. It's easier to change/adapt my vocabulary than it is to change my accent.
I love language, I do a lot of reading, and it's a delight when you find the right word that precisely expresses what you're thinking. Reading a lot expands your vocabulary and improves your adeptness at deploying it. When done in moderation, using puns and subtle literary references is fun (even when no one picks up on it) - as long as it doesn't detract from the actual message I'm communicating.
1. I do not mean speaking like the Architect from The Matrix here. The other week, I was called out by a monolingual collegue for using "nomenclature" rather than "naming convention" or "naming system" - which feel kludgey to me. Also, when I do make the effort to use shorter words after thinking of a long one first, that adds brief pauses to my speech, which gives the appearance of an ineffective communicator.