It still is a problem in general, that's why fonts now have webassembly in it.

This repository has a good outlook: https://github.com/harfbuzz/harfbuzz-wasm-examples

The fact that the article was able to show correct version in regular text is pretty good indicator that if done correctly those are more or less solved problems. I don't disagree that there are probably plenty of times when those mistakes are repeated and solutions not used widely enough (more often for Arabic scripts than other languages), but even for 2017 it feels more like anecdotal examples of what can go wrong ignoring existing technical details. But those mistakes largely come down to having someone who cares and understands the language and technology not for the lack of solutions. There are probably plenty of interesting edge cases that might not be handled perfectly even though solutions for basic cases exist, but article doesn't come even close to discussing those technical details especially if it's only conclusion is "computers introduced more problems, notably because of Unicode".

> The inflexibility persisted and has arguably only become more aggravated in the 20th century

What about 21th century? Digital printing can overlap characters just fine. And modern fonts support context sensitive ligatures and glyph substitutions.

Second/third example those seemed to be caused by more by someone who doesn't understand the language copy pasting stuff.

PDF -> that's just PDF being bad. Text and text search in PDFs tends to mes up even or English.

> with unicode number U+0623, but one can also type أ, which is an alif and a high hamza, represented by unicode numbers U+0627 and U+0654.

That's what Unicode normalization and locale settings are for. Same thing applies to large fraction of latin based scripts other than English, anything which has letters with diacritic marks.

> for كثيره and كثيرة will in most cases yield different results

Similar thing in almost any non English language for example cafe and café or ABC and ⒶⒷⒸ. Although at least some systems handle it reasonably. Not sure how much it is heuristics based on large data (hard to scale across software), and how much it's good application of Unicode character decomposition/normal form tables. Which Arabic letters lack appropriate Unicode decomposition (and other) tables and what are the best practices of unicode normalization/decomposition/locale handling for search (applicable for all languages) are more interesting and actionable topics.

> Not even the simple idea of CJK has been implemented.

Many users of CJK language would argue that CJK unification was a mistake. If different languages prefer different forms of the glyph, they should better be separate characters. Having separate Chinese and Japanese fonts because CJK unified too much just introduces additional points of failure.