Wikipedia:Styletips/23

Quotations: allowable typographical changes

Although the requirement of minimal change in direct quotations is strict, a few purely typographical elements of quoted text should be conformed to English Wikipedia's conventions without comment. These include the following:
 * Use the style chosen for the article: unspaced em dash or spaced en dash.
 * Set apostrophes and quotation marks straight, not curly.
 * Remove spaces before punctuation such as periods, colons, and %.
 * When integrating the quotation into the grammar of a larger sentence, downcase the first letter of a quotation that is in upper case purely because it starts a sentence in the source (It turned out to be true that "a penny saved is a penny earned").

But generally preserve bold and italic face, and the variety of English.

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