"Correct" English is a different matter - it serves no higher purpose than to keep you in your place.
Using incorrect language, however, makes whatever you are writing about seem less thought-out or even just plain wrong.
Have you ever read 4chan? You can argue that that's English, since it's English speakers using the English language... but you will surely agree that their version of English makes them look like uneducated morons, even without considering what they are trying to say.
Anyway, the style guide here suggests that authors use the clearest word to describe a given situation or quality. I don't see anything wrong with this -- clarity is always good. (Your writing could still be understandable without using the words correctly, but why use incorrect words just because some other people are also wrong?)
The thing that comes to mind here is the notion of a "controlled vocabulary" from library science. When you're building a hierarchical model of concepts (Library of Congress, or Dewey Decimal Classification) it helps to have a relatively small and consistent set of identifiers so that you can consistently refer to the same thing.
I think of good English usage as being similar. When what you mean is X, use the word for X. So these sorts of lists of usage can be thought of as a mapping from concepts to words.
English is dynamic, true, but you have to remember that when you talk about "English is what English speakers speak" I think you have to also consider, to avoid a grave disservice to history, that "English speakers" mean not only those walking around today, but all the vast collection of written words through the ages.
Nice point. It's backcompatibility with legacy uses (use is a synonym for application.) And so the familiar battle between current usage and backcompatibility plays itself out in this arena, with the familiar casualties of irregular special cases, unconceived foundations and unretractable experiments.
It all depends on the sense with which you approach something. I have been a loyal reader of the Economist for a decade now, and have arrived at the point of finding competing publications almost unreadable due to the poor standards of writing and the substitution of affectation for real style.
On the other hand, I also enjoy reading 4chan and post there occasionally - sometimes in clear English, sometimes in LOLspeak. Though many there are undoubtedly only semi-literate, many others are simply having fun at the expense of others (as can be seen by the relatively correct use at Encyclopedia Dramatica). If you use the 'wrong' misspellings at 4chan - I kan has chisburgar, say - you'll just get laughed at.
You criticise 4chan speakers as sounding uneducated. That's a judgment about class, not content. Do you really think the purpose of education is class mobility, rather than, say, argumentative, expositional, philosophical and technical knowledge and skills? A criticism that their writing as uninformed, uninteresting and pointless would have more substance (which you imply with "morons".)
I agree that if one wants to impress others, perhaps seeking preferential favour, one had best take care to sound "educated" (for that specific aim, it doesn't matter whether one actually has the knowledge and skills of education, since it's just about appearance). If one seek to communicate with others, to relate, to collaborate, to share information, clarity is more important than sounding educated.
Of course, arbitrarily humpty-dumpty incorrect usage will confuse listeners, but the style guide fusses about what "acronym" and "alternative" mean, strictly and technically. Can you give an example where the specific incorrect use they mention is less clear?
BTW: I probably should have replied to the top comment about "acronyms".
Where does it say to "use the clearest word"? The word "clear" doesn't come up when I search for it on that page...
You're probably already read Orwell's piece at some point - if not, have a look, it's great.
To be fair, the guide doesn't outright state "use the clearest word", but the implication's clear; the entries for pressurise and for critique, for example.
Using incorrect language, however, makes whatever you are writing about seem less thought-out or even just plain wrong.
Have you ever read 4chan? You can argue that that's English, since it's English speakers using the English language... but you will surely agree that their version of English makes them look like uneducated morons, even without considering what they are trying to say.
Anyway, the style guide here suggests that authors use the clearest word to describe a given situation or quality. I don't see anything wrong with this -- clarity is always good. (Your writing could still be understandable without using the words correctly, but why use incorrect words just because some other people are also wrong?)