So now apparently this bug, or just me doing it wrong, has been fixed and we can effectively edit a formula just by moving with left and right arrow keys. The only quirk is that I'd like to have some more precision as to what to edit. For example if there is a range a1:a10 and I want to edit only the second element and replace it with a11 for example I'd have to remove the full range and start over. After maybe sighted people have the same problem too although I doubt. But probably the best patch of sequoia yet despite the little new bugs here and there is that we can finally edit a cell's content again just by pressing vo-space on it instead of having to root the mouse and then perform mouse click, vo-shift-fn-5+vo-shift-space.