I read with interest that WordPress 4.9 is going to protect site owners from
themselves fatal errors resulting from the direct editing of files.
That's really good news!
I know I shouldn't but I edit my site live - I just can't be bothered with setting up a test environment, making changes and then copying them across.
There's been many an occasion where I've made a mistake, mistyped, forgotten a bracket or semi-colon, or simply screwed up.
Some may say it's just going to encourage bad habits (maybe so) but having WordPress refuse to save the file when a fatal error would occur is brilliant.