I offer this advice with some trepidation, as I am opening myself up to scrutiny and risking the possibility of someone finding flaws in my reasoning. If you do have a comment, I would be interested to receive it.
“From an early stage in my career, while still a research assistant in Leicester Polytechnic’s life sciences department, I realized [1] I had a keener eye than other people for mistakes in written work. In those days, articles were drafted in pen or pencil and handed over for typing. Some of the Department’s [2] secretaries asked me why the articles they typed for me always came back with corrections, when everyone else seemed to be perfectly happy with their work.” [3]
“The ability to see written works [4] flaws has been a bit of a curse. I did consider whether I should ignore mistakes to keep the peace: or [5] perhaps mark-up [6] only a percentage of them. For my colleagues, wherever I have worked, finding a typo in one of my messages has always been a great cause for celebration.
[7] ”Although I was absolutely confident that no error – in spelling, grammar or punctuation – [8] would escape me, I realised as the years passed that there were far more style rules, conventions and questions of choice than had ever been taught at school. Some of them have rarely, if ever, been written down for reference. I investigated each issue and logged my conclusions, mentally, for use in future adjudications. This has been a continuing quest, in the light of constantly-changing [9] ‘rules’ and fashions”. [10]
[1] The fashion in UK English is to use s rather than z for words ending in ‘ise’, ‘ised, ‘isation’ etc. But watch out: if your spell check is set to US English it will want you to use z.
[2] Inconsistency in use of upper and lower case. The writer used lower case for ‘department’ earlier in the same paragraph. Neither is wrong, but you need to choose whether a word or term will be in upper or lower case and stick to your decision consistently.
[3] The quotation isn’t finished yet, so there shouldn’t be closing quotation marks at the end of this paragraph. If a quotation extends over more than one paragraph, each one should start with opening quotation marks but only the last one should have closing quotation marks.
[4] There’s an apostrophe missing here. Assuming that the sentence is about flaws in, of or pertaining to written work, it should be: written work’s flaws. If it’s about written flaws in, of or pertaining to written works (plural), it should be: written works’ flaws.
[5] Inappropriate use of a colon (:). A semi-colon (;) might have been nice to use there. Semi-colons are often useful to break up a sentence a bit without dividing it into two separate sentences. A colon (:) tends to indicate that something is about to follow. Often this is a list (e.g. ‘the available punctuation marks include: full stop, comma, semi-colon and colon’) or a piece of information that the first part of the sentence has led you to expect (e.g. ‘my rule is this: never use a colon if you don’t know what it’s for’).
[6] Incorrect use of hyphenation. When you mark up a document, you are doing a mark-up. In one case it should be hyphenated and in the other it shouldn’t. If you say that sentence out loud, you should find that you automatically run the two words together in the case of ‘mark-up’ (creating, in effect, one word) but you take a little longer to say the separate words in ‘mark up’. There are many cases where the context in which they appear dictates whether two particular words will be hyphenated.
[7] These quotation marks are upside down and back to front. Normally your computer will automatically use the correct marks, but sometimes things can go astray. Traditionally, the opening ones look a bit like 66 and the closing ones are a bit like 99 – although in some of today’s fonts they have lost their ‘tadpole’ shape.
[8] That should have been a dash, not a hyphen. A dash is longer – like this. The first dash in the sentence was delivered beautifully – and automatically – by the computer as the sentence flowed onto the page. But if a sentence is tampered with afterwards, you need to make sure the computer knows that it’s a dash rather than a (shorter) hyphen that you want. It may be necessary to retype the last letter of the word before the dash to do that. Then as long as you use a space before and after it, the short hyphen (-) that initially appears will extend into a dash when you start on the next word. If all else fails, copy and paste a dash from somewhere else on the page.
[9] Normally you don’t need to use a hyphen to connect an adverb (often ending in -ly) with the verb to which it adds extra description. When using something other than an adverb, you do (e.g. market-changing innovations). Watch out for the adverb ‘well’, though. Note the difference between a well-considered application of it and an application that is well considered.
[10] In this case the full stop should be inside the quotation marks as it is part of the sentence being quoted. The same would not be true if you were quoting an extract from within a sentence, e.g. the bit about “finding a typo”.
Contact: Mark Nicholson Copywriting
Email: mark@mncopywriting.com
nicholsonmark60 
Comments posted by Lee Prior Collier (moved to test answers page):
realized in UK paragraph
department -> Department
while -> whilst
no comma needed after “In those days”
work’s flaws
No end ”
peace: should be ;
should be .” not “.
Thanks, Lee, for being first to comment. You’ve scored 7 out of 10, I think. I’m assuming that you mean the inverted commas should be deleted from the end of para 1, not added to the end of para 2. While/whilst is a matter of taste, to me. Does anyone disagree or have a rule on that? There does need to be a comma after “in those days” because in this particular passage I want the reader to pause at that point.