This is a list of accepted changes to block quotes that are difficult or impossible to achieve with the current definition of <blockquote>. For more information please read the accompanying article Blockquote problems and solutions.
The Chicago Manual of Style 15th edition covers quotations and dialogue in chapter 11. Changes to block quotations it discusses include (mainly from 11.8):
Changing quotation marks e.g. from single to double
Changing the initial letter case, e.g. from capital to lower case
Changing or omitting punctuation at the end of a quotation or beside ellipsis points, e.g. from a period to a comma
Omitting notes and note reference marks in the original, unless this affects meaning
Adding note references
Correcting obvious typographic errors silently, although “the reader must so be informed in a note, in a preface, or elsewhere”
Indicating typographic errors (intentional or otherwise) in the source using sic
Changing archaic ʃ to s, v to u etc.
Adding bracketed adjustments to the original quote (to indicate changed tense, capitalisation etc)
Adding stage directions, description, interjections (such as laughter) etc. to a dialogue or interview that may not be present in the original, especially if the source is a performance, movie, debate etc.
Adding ellipses to indicate the omission of a word, phrase, sentence or more from the passage quoted
Insertions to clarify meaning and provide missing words or letters, or clarify a translation with the original word or phrase
Noting stylistic changes such as the addition of italics to emphasise part of a quote, or conversely to point out that the italics were present in the original
In addition, quote metadata may appear at the end of the last line or immediately below (but visually associated with) a block quotation, including:
Attribution, as a full citation, short citation, or shortened reference such as page number
Notes regarding author changes, the quote’s source material, small print etc.
Examples of inline quote metadata in the Chicago Manual of Style include:
Bracketed and italicised notes describing the difference between two versions of the same block quote (11.14)
Inline short citation (11.17, 11.26)
Inline full citation (11.73, 11.81)
Page number as a shortened reference (11.82)
Adding intervening text mid-quote in brackets (11.26)
Italicised stage directions, with and without parentheses, in a dramatic transcript (11.49)
Italicised, bracketed interjection in an interview transcript (11.50)
Ellipses to indicate missing prose (11.55, 11.57, 11.60, 11.61)
Brackets to indicate change in capitalisation (11.63)
Ellipses to indicate the beginning and end of a a quotation (11.65)
Bracketed notes to annotate missing, guessed at or illegible words, along with ellipses or 2-em dashes to indicate gaps (11.66, 11.67)
Insertions in brackets to clarify meaning and provide missing words or letters (11.68)
Italicised sic. in brackets to indicate a word intentionally misspelled in the original (11.69)
“Italics added” appended to an inline citation, and added as a bracketed note inline immediately after the italicised text (11.70)
Examples in the Chicago Manual of Style of quote metadata on a line immediately after the block quote, but being visually associated with the block quote (e.g. sharing the block quote’s font-size, font-family, and/or line-height, line break after metadata but not before to visually separate from following prose etc) include:
Short citation (11.28, 11.40, 11.83)
Shortened reference (11.84)
Translation of foreign language quote in square brackets (11.87)
The following Shakespeare examples are all sourced via the links at General Shakespeare Criticism, and are styled to match the source. Suspected changes and additions to the source material made by original authors are <mark>ed. Most of these are impossible to achieve in compliance with the current spec.