A good rule of thumb is that changes to quotations are not permitted, period. So much is at stake when we present the words of someone else, whether spoken or written, and responsibility lies with the quoter to render what was said accurately and in a fair context. The actual wording of the quotation must be reproduced exactly. Yet CMOS 13.7 lists half a dozen things that are OK to change when quoting.
A look back to 1906, when the more straitlaced 1st edition of the Manual offered intriguing punctuation!, puzzling spaces ?, and curious examples . . .
Add a note citing a source (1) whenever you write something that isn’t common knowledge and (2) whenever you . . .
A look back to 1906, when the more straitlaced 1st edition of the Manual offered intriguing punctuation, puzzling spaces, and curious examples . . .