It rather means that case operations are locale-specific. This is indeed unfortunate, as Unicode tried hard to split characters that look same or similar but ha

It rather means that case operations are locale-specific. This is indeed unfortunate, as Unicode tried hard to split characters that look same or similar but have different behaviors like that, but inevitable because Turkish (among others) is otherwise using normal Latin characters. In the other words, Turkish speakers are unconsciously mixing Turkish `i` and normal Latin `i` in their texts and there is no way to separate them after the fact [1]. [1] See https://unicode.org/mail-arch/unicode-ml/Archives-Old/UML009/0619.html https://unicode.org/mail-arch/unicode-ml/Archives-Old/UML009... and https://unicode.org/mail-arch/unicode-ml/Archives-Old/UML009/0624.html https://unicode.org/mail-arch/unicode-ml/Archives-Old/UML009... (and especially note the transcoding issues)