The New Yorker style guide – leaked

Got my hands on a copy of the New Yorker style guide, a top secret document whose arcane mysteries have baffled all but a very select few. The New Yorker has the greatest copyediting (subediting) department in the known universe. These are their sacred texts. Be careful reading, there's no guarantee you won't end up like the Nazis at the end of Raiders of the Lost Ark.

General notes
In general, for style, grammar and spelling guidance, imagine it's 1823.

coöperate
Write coöperate with a diaeresis over the 2nd o. This shows there's a hyphen missing. No, I don't know why we don't just have a hyphen. If we didn't have the dots, people might think we didn't know how to spell cuperate.

cuperate There's no such word as cuperate.

diaeresis
Turns out the diaeresis in coöperate comes from Afrikaans. And New York used to be called New Amsterdam, OK?

Dutch
I was talking about the Dutch. Keep up. And it's not from Afrikaans, it's a pronunciation guide mark.

élite
With pronunciation guide mark. It's easy to spot the élite, as they are the type of person who write it like that.

hyperbole No pronunciation guide marks.

Internet Cap up. Because someone's got to. Also, just because we have given up and admitted the web exists, doesn't mean we won't stick a banner on the site that obscures four lines of text.

numbers
Write out all numbers in full. And then add some more letters. Yes, even dates. OK, not dates, but THAT'S IT FOR SLACKING. However, whenever you write a year in figures, add a couple of commas. As a sort of consolation.

pronunciation
Have you ever noticed that pronunciation isn't pronunciated the way it's written?

punctuation
All punctuation goes inside quote marks, even if it's from a different sentence.

teen-age
We must never, ever forget that these are two separate words

traveller
Words such as traveller and focussed have double consonants. Sometimes this is because that's how they are spelled.

writing to length If an article is going fine, and saying everything it needs to say and looks great, add 10,000 words to it.