"Automatic spell-checking is only turned on for text boxes containing more than one line, where you can enter as much text as you want."
This line in the support-article for spell-checking implies as I understand it, that spell-checking is only active (if activated) in text fields without character-limitation. This seems to be the case.
The problem is, that my dyslexia doesn't care about the possible length of the text I am about to write.
Problem
Spell-checking, though activated, does not work in all text-boxes. It seems to work in only a very specific case of text-boxes. This is especially a problem for people with dyslexia (like myself).
Solution
If spell-checking is activated, please let it do it's job everywhere!