2. Never use a long word where a short one will do.
3. If it is possible to cut a word out, always cut it out.
4. Never use the passive where you can use the active.
5. Never use a foreign phrase, a scientific word, or a jargon word if you can think of an everyday English equivalent.
6. Break any of these rules sooner than say anything outright barbarous.
-- Orwell, "Politics and the English Language"
The thing is, note "will do" in (2). There are many cases where a short word really won't do, lest you lose nuance and meaning.
Taking, as an example, the final sentence of your first paragraph: "Brobdingnagian, deleterious, autodidact, loquaciousness... are these really such strange vernacular?" we find a sentence that is grammatically incorrect, with the singular form of vernacular. Assuming a typographically damaged plural does no good, as these words are not vernaculars. We do no better with the assumption of an elided indefinite article ("are these really such [a] strange vernacular?") as the answer is trivially yes, attempting conversation using only these words (Brobdingnagian, deleterious, autodidact, and loquaciousness) would be an exercise of Cnutian futility. As the recurring problem in finding meaning in this sentence is this definition may I suggest that perhaps the primary issue is in the choice of words? I would suggest the substitution of "words" in place of "vernacular", as this recovers a perfectly sensible rhetorical question. Perhaps, in keeping with the theme of subtle distinction in word choice, "obscure" could be substituted for "strange", signifying the strangeness is rooted in rarity of use, rather than e.g. etymology.
Although we might get a bit of a thrill from talking over people's heads, it doesn't really mean much of anything. And all it takes is one misuse -- for example, calling Brobdingnagian a neologism -- and we tear ourselves down more than we could hope to build ourselves up.
Agreed - never use a complicated word when a simple one will do - but you either have to turn verbose or lose nuance, as we're not talking synonyms, but words which have meanings distinct from some of their more commonplace counterparts.
No thrill, I just hate taking the colour out of language, and I like to share words far and wide, so they don't drift into oblivion, along with the thought and meaning behind them.
It's true that there are sometimes nuances lost in the conversion from large to small, but there is far more nuance lost once your partner doesn't know what the hell you are saying. For you, Brobdingnagian might have some special nuance (I'm picking on that word because it is ridiculous to me), but to your partner it has no nuance or flavor -- they have no associations with that word, nor any grasp of any subtleties of meaning -- in fact they don't grasp the meaning at all. So if you are trying to get something across, it's simply a bad way to do it.
I mean, don't get me wrong -- I don't want to deride big-word-users. If you want to do to because you like it -- that's obviously fine. Also, if someone does happen to have a thing with Brobdingnagian, I guess you might have just made their day a lot better. But at some point, you have to acknowledge that obscure vocabulary is more of a hindrance than a boon to communication.
Children may be precocious and tolerable. I recall the joy of finding new words - grownup words. Most people find it pretentious and condescending in adults. It is poor communication. Want a game of who can think of the most obscure word? Firstly I tried 'widdershins'. Let's exclude Brobdingnagian as an obvious neologism. (Not trolling - really can't see why you think it ain't?)
Nah. I'm proud to say I got everything except Brobdingnagian, which on further investigation is more of a literary reference than a "real" word.
I suppose this is what happens when you spend your formative years buried in literature - it probably doesn't help that I mispronounce all sorts, as books make poor elocutionists.
I do worry that as we further and further consolidate our vocabulary that we lose the breadth and depth of thought that nuanced words provide... so did Orwell...