There is no unjoined form of Arabic. The Arabic script became Arabic when Nabataean script started developing joined letter forms. Unjoined Nabatean is as foreign to Arabic as Phoenician is to Greek.
It does if one is doing typesetting math-heavy documents. Nothing really matches TeX quality or flexibility in math typesetting, not even typst (yet, at least).
In some countries, legal documents are required to not have any paragraph breaks, so you can have a document with one paragraph spanning 100s of pages. OpenOffice has a hard limit of 65534 per paragraph, and it took LibreOffice quite some work to left it: https://bugs.documentfoundation.org/show_bug.cgi?id=30668
The fix looks like a 5 line fix because it is a last step in a very long process of optimizing LibreOffice text layout that started years ago. This 5 line fix could not have been possible 10 years ago simply because the code it is fixing didn't exist back then.
In Arabic, Mercury (planet) and mercury (element) are two different words (عطارد and زئبق), here the machine translation is using the wrong mercury for the context.
Photoshop relatively recently consolidated its text layout into a single layout engine (based on HarfBuzz) and Arabic support no longer an opt-in (which was the source of the trouble, you had to know you need to opt-in Arabic support before installing the application)
That is not the point I’m making, rather a single person is responsible for how most of software render text in most of the world writing systems and no one is wondering how 6 billion people on this planet so much depend on the work of “this one guy”. It is because text layout is something 99% of software developers can’t do right if their lives depended on it (same for anything that involves the irregularities of human nature, software developers are not cut for this).
Reem Kufi designer here, that is the original form of ع in Arabic and the only form used in manuscript Kufi. Kufi-inspired typefaces often use the more familiar form from later calligraphic styles. Reem Kufi has an alternate form as well, but it is not the default.
I strand by my comment. Replicate core TeX (and LaTeX) core features is easy (text layout, hyphenation, line breaking, math typesetting, etc. all are solved issue, often with many independent implementation that are as good as TeX‘s if not better), the issues that holds most people are packages and decades of TeX/LaTeX legacy.
I can count like half a dozen TeX/LaTeX alternatives (SILE, Patoline, Platypus, Lout, some are more dead than the others) without even looking them up. It is easy to make a TeX/LaTeX alternative, it is hard to get people to use it.
Math is taught in Arabic, using Arabic notation and written from right to left in many Arabic countries. That is basically the only form of math I’m personally familiar with.