Cherokee Numerals

To make matters more confusing, modern Arabs don't use the numerals we call "Arabic": https://en.wikipedia.org/wiki/Eastern_Arabic_numerals

There are however Arab regions where it is more common to see so-called "Western/Arabic" numerals used instead of the native-Arabic-script numerals. This is the case of Morocco, for instance.

As I explained in more detail in https://news.ycombinator.com/item?id=26525109, those are "Western Arabic" numerals, not "Western/Arabic" numerals, because they were invented by the Arabs in Morocco and thereabouts, which is to the west of the Arabs in, for example, Syria.

Morocco today doesn’t use its native Arabic numeral system that diverged from that used in other Arab countries to the east, it uses the European system borrowed wholesale.

It's just a minor typographical variation, similar to how some lowercase "g" glyphs have a closed loop while others have just a hook, or how some Latin fonts have serifs and others don't. It's not a totally different numeral system like the Greek or Maya systems, or even a dramatically different set of glyphs like the Eastern Arabic or Brahmi numerals.

The old African numeral glyphs resemble today's European styles more closely than Caslon resembles blackletter, more closely than either resembles Palmer cursive, and more closely than any of the three resembles Roman monumental inscriptions (except, of course, for the upper case of Caslon). Yet we consider Caslon, blackletter, Palmer, and the inscriptions all to be the same Latin alphabet.

Again, Morocco uses the European system wholesale, not just local glyphs that bear a great resemblance to European glyphs. This development is a consequence of the French colonial era and the fact that most serious printing in the country is done in French, while Arabic is mainly (though not exclusively) treated as a language only of speaking and non-serious writing. Thus, even when Moroccans do write in Arabic, they use the same numbers known from French-language publications.

Sure, but French uses the Moroccan† system wholesale, a consequence of developments predating the French colonial era. So Moroccans writing in Arabic have been using the same numbers known from French-language publications for some five centuries longer than the French-language publications have been using them, and some seven centuries longer than the cultural hegemony of French in the country. There wasn't some time in between when Moroccans were using Eastern Arabic numerals or classical Greek numerals or something.

Suppose you find that an Italian professor of computer science has published a computer science paper in Italian using Knuth's cmr10 font from California. Moreover, he has previously published papers in English, some also using cmr10, in part because he wants people in California to be able to read them, and Italian is mainly treated as a language of speaking and non-serious writing — or at any rate not for computer science.

Would you therefore say, "Italy today doesn't use its own native Latin alphabet that diverged from that used in Greece; it uses the Californian system borrowed wholesale, not just local glyphs that bear a great resemblance to Californian glyphs"? To me this sounds absurd, even though the cmr10 glyphs being used were designed in California.

(Perhaps the answer in this case is too obvious because "cmr10" is an abbreviation for "Computer Modern Roman 10 point", and Rome is in Italy, but on the other hand, we are discussing a system of numerals almost universally known as "Arabic".)

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†At the time that the French adopted it, political boundaries in the Maghreb were of course very different, so at the time Fibonacci might have said his numbers were the numbers used in the Almohad Caliphate; but before the Almohads conquered the Maghreb and al-Andalus, they were the Berber rulers of Tinmel, so I don't think it's a stretch to call them Moroccan. The numerals were already in use throughout the Maghreb before the Almohad conquest, though.