Great article! Beautifully written, and wonderfully interesting.
Just a small note about Spanish: Even if they aren’t necessarily extra letters, Spanish does incorporate accented letters pretty heavily into it’s written form (á, é, í, ó, ú, ü). It also uses those funny upside down exclamation points and question marks (¿, ¡), and has a few of those two-characters-as-one-character oddities (ch, ll).
Anyway, overall a great article! Just had to speak up for the language of my people.