Because the apostrophe as used in English is a punctuation mark, not a letter, and especially not a modifier letter. The author argues that any name ought to be matched by anything in \w, and we should avoid a punctuation character for that reason, but he doesn't mention other punctuation marks like the hyphen that also commonly occur in names.

> And I fully agree with footnote 2, why is an extended Unicode character being used in place of the apostrophe?

Some reasons:

> The Unicode character ’ (U+2019 right single quotation mark) is used for both a typographic apostrophe and a single right (closing) quotation mark.[1] This is due to the many fonts and character sets (such as CP1252) that unified the characters into a single code point, and the difficulty of software distinguishing which character is intended by a user's typing.[2] There are arguments that the typographic apostrophe should be a different code point, U+02BC modifier letter apostrophe.[3][better source needed]

> The straight apostrophe ' (the "ASCII apostrophe", U+0027 ' apostrophe) is even more ambiguous, as it could also be intended as a left or right quotation mark, or a prime symbol.

* https://en.wikipedia.org/wiki/Right_single_quotation_mark

* https://en.wikipedia.org/wiki/Apostrophe#Unicode

The Unicode Standard states that U+2019 RIGHT SINGLE QUOTATION MARK is the preferred apostrophe character.

    0027 APOSTROPHE
    [snip]
    * 2019 is preferred for apostrophe

First: no, that reasoning doesn't generalize nearly well enough. Unicode has many quotation marks, and " is just one of them. “ and ” are perfectly acceptable to use to wrap double-quoted text and you can't say they "should" use ordinary " and a proper font, because a font doesn't know which one is the beginning and which is the end of the quoted text. (Hence why those characters even exist).

Second: no, Unicode definitely considers other characters to be apostrophes:

    >>> unicodedata.name(chr(700)) # https://en.wikipedia.org/wiki/Modifier_letter_apostrophe
    'MODIFIER LETTER APOSTROPHE'
    >>> unicodedata.name(chr(1370)) # https://en.wikipedia.org/wiki/Armenian_(Unicode_block)
    'ARMENIAN APOSTROPHE'
    >>> unicodedata.name(chr(2036)) # https://en.wikipedia.org/wiki/N%27Ko_script
    'NKO HIGH TONE APOSTROPHE'
    >>> unicodedata.name(chr(2037))
    'NKO LOW TONE APOSTROPHE'
    >>> unicodedata.name(chr(65287)) # https://en.wikipedia.org/wiki/Halfwidth_and_fullwidth_forms
    'FULLWIDTH APOSTROPHE'
    >>> unicodedata.name(chr(917543)) # https://en.wikipedia.org/wiki/Tags_(Unicode_block)
    'TAG APOSTROPHE'

For that matter, there's a "Greek question mark" (https://en.wikipedia.org/wiki/Question_mark#Greek_question_m...) which is semantically equivalent to ? for Greek text, but rendered identically to ; in most fonts. And there are some CJK ideographs (https://en.wikipedia.org/wiki/Ghost_characters) which represent completely fake characters not used in any writing (including in any other East Asian language), which were included in an old Japanese character standard by mistake and then copied into Unicode.

"Unicode only has one" is the start of a lot of false claims. It is very much "designed by committee".

> Unicode has only one apostrophe. The same one as ASCII apostrophe. The problem here is people using right single qoute as a "fancy" apostrophe when they should be using a font that renders apostrophe in the desired way.

No, the ASCII ‘quotes’ are inch and foot markers. Relying on a font to render the the inch and foot markers as quotes is a … unique … approach.

> I have to fix this junk all the time in CD-text and Musicbrainz metadata.

Wait, are you the guy whose Musicbrainz titles are constantly replacing my carefully- and properly-punctuated ones every time I sync? I beg you to reconsider.

> Unicode has only one apostrophe.

Two code points have "apostrophe" in their name, U+0027 and U+02BC:

* https://en.wikipedia.org/wiki/Apostrophe#Unicode

There is also a third which is often used, U+2019:

> The Unicode character ’ (U+2019 right single quotation mark) is used for both a typographic apostrophe and a single right (closing) quotation mark.[1] This is due to the many fonts and character sets (such as CP1252) that unified the characters into a single code point, and the difficulty of software distinguishing which character is intended by a user's typing.[2] There are arguments that the typographic apostrophe should be a different code point, U+02BC modifier letter apostrophe.[3][better source needed]

> The straight apostrophe ' (the "ASCII apostrophe", U+0027 ' apostrophe) is even more ambiguous, as it could also be intended as a left or right quotation mark, or a prime symbol.

* https://en.wikipedia.org/wiki/Right_single_quotation_mark

Martine [1] is a series of French-language children's book. They have simple titles like "Martine à la ferme" (Martine at the farm) or "Martine fait du camping" (Martine goes camping).

"Martine écrit en UTF-8" is what you get if you interpret the UTF-8 string "Martine écrit en UTF-8" (Martine writes in UTF-8) as Latin-1. It's not as common as it once was, but that kind of encoding issue used to be encountered fairly often by French speakers on the Web.

[1]: https://en.wikipedia.org/wiki/Martine_(character)