[Tex2002ans]

Originally Posted by Quoth

What's best typographic practice for identical list items?

In English, when writing a "ditto character", it should be 1 or 3:

• " (U+0022) = Straight "dumb" quote.
• ” (U+201D) = Right "smart" quote.

(I always use RIGHT DOUBLE QUOTES.)

Originally Posted by Quoth

Or is there an actual ditto character used in typesetting before unicode etc that's in common unicode fonts?

Hmmm, never thought of it.

But after doing some quick research, it does seem like there's an actual:

• 〃 (U+3003) = DITTO MARK

but this is ONLY meant to be used in CJK (Asian) texts.

* * *

Side Note: For the actual technical information on that, see:

• https://www.unicode.org/Public/14.0....Extensions.txt

That Unicode file describes:

The Script_Extensions property indicates which characters are commonly used with more than one script, but with a limited number of scripts.

and lists:

3003          ; Bopo Hang Hani Hira Kana # Po       DITTO MARK

which means only used in these writing systems:

• Bopomofo
• Hangul
• Han ideographs
• Hiragana
• Katakana

See also:

• TeX Stack Exchange: "Is there a ditto symbol?"
• Fileformat.info: "'DITTO MARK' (U+3003)"
  
  • This character is listed under the "CJK Symbols and Punctuation" block.

Originally Posted by Turtle91

I’m definitely not an expert… but I’ve only ever seen the standard straight double quote.

And I've mostly seen the RIGHT DOUBLE QUOTE.

Only time I recall seeing the straight was when digitizing typewriter material.

Originally Posted by Quoth

So perhaps in English the closing double quote is best, or italic straight double quote " if ” looks strange in the current font.

No. Never use <i>italics</i> for meaningless information like this.

Remember the latest discussion:

• 2021: "Italics and Bold"

Italics and emphasis has a purpose.

You don't just go marking them up "because you want it to show in italics".

Just like you don't go marking text with <h3> "just to make it bold and slightly bigger font"!

Originally Posted by Quoth

Apparently it's better style to repeat the information (Oxford guide)or use "do." as an abbreviation of ditto.

Using any sort of "ditto" in ebooks is... debatable, because of Accessibility.

So much of ditto's usage is dependent on visuals + vertical alignment. And, in ebooks, you can't guarantee the duplicate text will be directly above/below each other.

Ditto can also occur in:

• tabular data
  
  • much more common.
• text
  
  • much more rarely.

Let's take care of the easy one first:

* * *

Dittos in Tabular Data

In this case, I'd still say using the "ditto quotes" would be fine.

I'd rule out "do."—it's antiquated. (Can't say I've seen it in any modern books.) I'd almost always replace that with the more modern quote marks.

Repeating all information, from an Accessibility standpoint, may be the best. But, from a visual/typographical standpoint, it can lead to tons of visual clutter + can harm table's readability/understandability.

Side Note: On alignment + spacing + reducing table clutter, see the famous GIF I linked to: "How to make your tables less terrible" + similar to the arguments I made in:

• 2021: "Formatting tables best practices"

And I highly recommend the absolutely fantastic book: "The Visual Display of Quantitative Information" by Edward Tufte.

Side Note #2: On a similar typographical note, you should use EM DASH and not a HYPHEN when dealing with "unknown/blank data":



* * *

Dittos in Text

This is where I would lean much further towards "repeat all the text" instead.

I've seen the "ditto symbol" used in:

• long lists
• poetry
• and even standard paragraphs.

One example can be seen in:

• TeX Stack Exchange: "Quote (ditto marks) to avoid repeating a text"

If converting this to ebook, write it all out:

<i>c</i> before <i>e</i> or <i>i</i> is pronounced as in <i>church</i>
<i>g</i> before <i>e</i> or <i>i</i> is pronounced as in <i>gin</i>

because, in ebooks, you'd never be able to guarantee:

• the first line will stay as a single line
• the vertical alignment of the words/characters
• the spacing on the "ditto quote"

Similarly, I've seen examples like this with ditto marks under each matching word:



And that, too, is problematic in ebooks for the same exact reasons.

I know it looks really ugly, and seems extremely repetitive/verbose, but in ebooks, you should repeat all the text in those cases.

(For example, Text-to-Speech will have absolutely NO IDEA what the heck to do with the text in the above 2 images.)