> 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.

There are a lot more tells than vocabulary. There's accent, even tone.

And, of course, there's the style of clothing, haircut, makeup, accessories, etc. Pretty much everything :-)

One interesting tell that I might have heard in Jamie Johnson's documentary "Born Rich" was talk of holidays.

If you talk about holidaying with one's family in some exotic locale or of having a summer home in the Hamptons, the person you're speaking with can surmise that you're not poor.

The rich kids in that documentary also regularly go out to bars and think nothing of spending hundreds or even thousands of dollars on champagne.

It's definitely not just about how one talks that signals to others that one is part of the upper class.. but once one is established as in the upper class, then things such as one's manner of speech might distinguish you.

I think the idea is not to perfectly blend in, but to get closer to that circle by being more relatable.

I still need to grow out of the opposite. I had a typical lowish middle class upbringing, not poor, but parents were teachers so I was ahead of most classmates just by being around that environment and reading a lot. Being a country town this of course attracted teasing. I learned to talk plain and dumb it down. It's still hard for me to talk otherwise, but writing is OK. Only the teacher saw that so I never changed how I wrote too much.