according to my understanding, when navigating by line in an editable text field using the down or Up arrow key on a Bluetooth keyboard, VoiceOver should read the whole line at the position where the cursor has landed. However, this is not always the case, at least in iOS 10.2 and more or less in earlier versions. Sometimes, for example, when standing on the beginning of the second line and pressing Up arrow to move to the beginning of the first line, , the first line is not read. The issue seem to happen quite randomly as you navigate back and forth within a text field.
In different apps, you might experience another different issues. For instance, sometimes in Microsoft Word, VoiceOver is not reading lines when pressing the Up or Down arrow even though the cursor is actually moving. Also, Alt + Left arrow, which should move to the beginning of the previous word and read it, does not work at all in Microsoft Word.
In Pages, there is a bug when after using the Command + right arrow to move to the end of line, first line of all paragraphs disappear for VoiceOver and last line of all paragraphs appear as if duplicated, though in real the text is not affected. This incorrect state can be repaired by pressing left or right arrow, for example. Also, sometimes, navigation by lines with up or down arrow doesn't read the whole line but only a part of it, however, if you press up arrow and then down arrow, the whole line would be read correctly.
Next, whereas Up or Down arrow should move by line and Alt + Up or Down arrow should move by paragraph, and this is how it works in Mail or Pages, this is not the case in the Notes app where Alt + Up or Down arrow reads a different paragraph than it should, seemingly at random. And Up or Down arrow reads the whole paragraph from the start to the end although the cursor is actually moving only by line within that paragraph. And one might find other or slightly different odd behavior in other cases and apps.
I think this is worth reporting to firstname.lastname@example.org but the main reason I am sharing this observation is that I would like to ask if you could recommend me an advanced text editor app which shows this behaviour the least. Specifically, I am interested if the navigation in text fields in Ulysses is also problematic like this, or if you know another good word processor which works better regarding this odd behaviour.