Question: I've noticed that man pages and other documents formatted by Unix utilities often use double backticks ```` followed by double single quotes `''` to wrap quoted phrases instead of the double quote character `"`. Single quotes are similarly replaced. Why is this?

Here are a couple examples, from the man page for `grep`:

```
 To find all occurrences of the pattern `.Pp' at the beginning of a line:

       $ grep '^\.Pp' myfile

 The apostrophes ensure the entire expression is evaluated by grep instead
 of by the user's shell.  The caret `^' matches the null string at the
 beginning of a line, and the `\' escapes the `.', which would otherwise match
 any character.

 The grep utility is compliant with the IEEE Std 1003.1-2008 (``POSIX.1'')
 specification.

```

Answer: 
The semantics and the usual glyphs for these characters have changed
(several times) during the last 50 years.

The six-bit predecessors of ASCII contained various multi-purpose characters,
including one single quote-like
character, which was used for anything that had some similarity with
a quote: opening quote, closing quote,
apostrophe, or (by overprinting) acute or grave accent.

ASCII introduced one more quote-like character, so that now we
had `'`, which was used as apostrophe, closing quote, and
acute accent, and ```, which was used as opening quote or
grave accent (the concrete glyphs differed in various fonts).

For some bizarre reason, ISO-8859-1 declared `'` to be an
apostrophe or undirected quote, declared ``` to be a
grave accent, added one more accent `´` (acute accent),
*and abolished overprinting* (so that the isolated accent
marks were now completely pointless). Later extensions (MS-Windows
codepages and Unicode) fixed this by introducing new directed quote characters
and combining accents.

What you see here is essentially a relict from ASCII times, when most fonts
had paired (slanted and/or curly) glyphs for `'` and ```.
Output like that is generated by `makeinfo` from [Texinfo](https://en.wikipedia.org/wiki/Texinfo) sources. Texinfo can also [render to other formats like PDF](https://en.wikipedia.org/wiki/Texinfo), so it needs to be more expressive than ASCII. Maybe to avoid throwing away semantics, `makeinfo` encodes quotes like that, so you can see what is opening and closing quotes.

Example: If you couldn't see the difference, I can imagine I'd be a bit confusing if you wrote some Texinfo source and relied on the quote difference being visible, because you would have previewed it as PDF. Because you never rendered with `makeinfo`, you'd never discover that it isn't readable, rendered like that.