Why the exception exists
The reason is worth understanding, because it explains when to reach for the exception outside government work. It is not an aesthetic choice.
Where a document quotes text that will be inserted, amended, or relied on word for word, a comma inside the marks becomes ambiguous. A reader cannot tell whether the comma is part of the material being quoted or part of the sentence quoting it. Moving it outside removes the ambiguity at the cost of an unfamiliar appearance.
Any document with the same property has the same problem. Contracts quoting clauses, specifications quoting standards, and briefs quoting statutes all face it, and the convention is a solution to a real difficulty rather than a house preference.
What may be changed silently, and what may not
This is where an editor's authority is narrowest in the whole trade. Editors Canada's definitions place the verification of quotations inside copy editing, and stop well short of licensing repairs to them.2
Editors Canada's copy editing standards ask an editor to verify quotations, and to query any errors within quotations so the original source can be checked.3 Query, not correct. A quotation containing an error is reporting what the source said, and repairing it changes the report.
That constraint reaches further than authors expect. A misspelling in the original stays. A date that is wrong in the original stays. A capital letter that does not suit the sentence around it is a matter for brackets rather than for silent adjustment.
What an editor may change is the apparatus surrounding the quotation: the introduction, the attribution, the placement, and the punctuation joining it to the sentence, according to whichever convention the document follows.1
The mechanical rules that get missed
Three rules get missed most often, and each is checkable by search rather than by reading.
Each part of an interrupted quotation begins and ends with quotation marks.1 "John," asked Henry, "why do you go?" Editors find the opening mark missing on the second part more often than any other quotation fault.
Nesting is limited. The GPO restricts quotation marks to three sets where possible: double, single, double.1 A passage requiring a fourth is usually a passage that should be set as an extract instead.
Quotation marks precede footnote reference numbers when the two occur together.1 That is a typesetting rule nobody remembers and every proofreader checks, because it is invisible until a page is set.
Permission is a separate question from punctuation
Length matters legally as well as typographically, and the legal side has no arithmetic to fall back on. Authors expecting a word count are looking for something that does not exist.
The United States Copyright Office states plainly that no formula ensures a safe quantity. No predetermined percentage of a work, and no specific number of words, lines, pages, or copies, may be used without permission on that basis alone.4 Fair use is decided on four factors weighed together. They are the purpose and character of the use, the nature of the work used, the amount and substantiality of what was taken, and the effect on the market for the original.4
An editor can inventory every quotation in a manuscript with its source and its length. Whether any of them needs clearing is a question for the author and, where the answer is not obvious, an attorney.
What EditFast does
We apply whichever convention the document follows and record it on the style sheet. We query rather than repair anything inside quotation marks, and we return the inventory of quoted material with the work.
Everything a client sends is treated in confidence, including drafts, source material, and correspondence. Our grammar and style work and legal and policy document editing are quoted on the whole document.
A writer unsure which convention applies has one question to answer first. Will anyone rely on the quoted words exactly as printed? If yes, the punctuation goes outside. If no, it goes inside, and the style sheet records the choice.