That's a very narrow view of the world. One example: In the past I have handled bilingual english-arabic files with switches within the same line and Arabic is written from left to right.

There are also languages that are written from to to bottom.

Unicode is not exclusively for coding, to the contrary, pretty sure it's only a small fraction of how Unicode is used.

> Somehow people didn't need invisible characters when printing books.

They didn't need computers either so "was seemingly not needed in the past" is not a good argument.

> That's a very narrow view of the world.

Yes, it is. Unicode has undergone major mission creep, thinking it is now a font language and a formatting language. Naturally, this has lead to making it a vector for malicious actors. (The direction reversing thing has been used to insert malicious text that isn't visible to the reader.)

> Unicode is not exclusively for coding

I never mentioned coding.

> They didn't need computers

Unicode is for characters, not formatting. Formatting is what HTML is for, and many other formatting standards. Neither is it for meaning.

> That's a very narrow view of the world.

But not one that would surprise anyone familiar with WalterBright's antics on this website…