Here's a recent answer by Ian Lang at Quora. Mr Lang has kindly given me blanket permission to use any of his answers I wish to use, on my blog.
The ticklish question was:

How much does grammar and proper language impact a person’s social and professional image? Is this a mark of socioeconomic class?
Answer by "Ian Lang, Former Oik (still quite oiky from time to time)"
The ticklish question was:

How much does grammar and proper language impact a person’s social and professional image? Is this a mark of socioeconomic class?
Answer by "Ian Lang, Former Oik (still quite oiky from time to time)"
Putting forward the same(ish) answer four ways then:
Ay-up, me duck, not half. You get them snobby gets what won’t even look at owt we’ve wrote down up here in t’ north cos it i’nt wrote like what they speak down in t’ leafy bits of Surrey.
It does, yes, some people look at a piece of prose and if they spot a gramatical error then they dismiss it. Typos are allowed as long as it’s clear it’s a typo (look at the word grammatical previously again).
All communications should be worded and punctuated correctly in order to portray a clear and professional image of the organisation. Please comply with the attached guidelines and templates.
Within the precepts of certain types of individuals who, having had made accesible to them the zeniths, apogees, and pinnacles of the academic world, and who pride themselves on the fact, knowing exactly where to put apostrophes, semi-colons, and all the other apparatus of substantive prose, and understanding the rules of adjectives, adverbs and the sundry paraphernalia of the craft of the wordsmith, will look down upon those who have not had such extensive groundings and will instantly rebut even the most reasoned piece if the i is not correctly dotted in the approved manner.
The first is my northern mode. I do this when I want to put forward a sarcastic rebuttal to anybody who thinks we here are a bunch of illiterate oiks.
The second is my plain English mode. I do this to explain things that may be quite complicated in terms that are clear to somebody who doesn’t know it terribly well.
The third is my corporate drone mode. I almost never do this because frankly it creates prose that grinds my gears. If you’ve ever read Orwell’s Nineteen Eighty-Four you’ll remember Newspeak. They pride themselves that the vocabulary is shrinking every year. I feel the same about corporate drone prose as Winston did about Newspeak.
The fourth is my over-educated-arse mode. I do this when somebody’s grinding my corn and trying to prove that they’re clever-clever and vocabularious. Don’t start with me sunshine, because if you do, I’m going sesquipedalian on your arse. If you carry on, I might even go dodecasyllabic, and then you’ll be sorry.
Everything thereafter (including this bit) is my normal mode. You’ll notice that I use a lot of contractions (you’ll, I’m, don’t) and inject a dollop of patois every now and then, and then slip into a bit of bathos. This is because I can’t bear any prose where the author has clearly taken pains to make his/her grammar, structure, and syntax as clever-looking as possible. It just comes out stilted and reads like the report of a village parish council meeting. Going the other way you get stream of consciousness writing, which is just a posh way to say “bloody mess”.
Now then. Imagine the above were all written by different people. What would you conclude about their standards of education, social class, and means of earning a living?
Oh yes. Grammar, spelling and punctuation can tell you much. But not when it’s in the hands of a wordsmith (which is the written equivalent of a gobshite), it can’t.