Your comments

I agree with Steven Lu, we have the same behavior for Command+Up / Down and Control+Up / Down, it would be good to have one set of keys replaced with page up / down action (Command + Up / Down ?)

Viewing invisible characters, especially spaces & tabs would definitely be a good feature, I'm using daily textastic for Python coding and am collecting quite a few unnecessary trailing spaces in sources (maybe an option to show only trailing ones ?)