The only time that askers get notified of an answer is when it's created - so if you ask a question which then gets an answer so you get notified. If that answer is edited, you don't get an alert about it - and that's always been the case as far as I'm aware.
With the addition of following, an asker (or anyone) can now follow answers to see if they've been improved - so if you ask someone to add additional details in a comment or ask them to clarify a point of confusion, if you also follow the answer you'll be notified if it gets edited. Otherwise, the only way you'd know about the edit is if you get pinged by someone to say that they've edited based on your comment.
As an answerer, if you want the asker or any commenters to be aware of changes to your answer, you'll still need to leave a comment which notifies them - particularly since you can't know whether they've followed the answer or not. The asker has no special status with respect to being notified for comments on the question's answers. In other words,
@<username> notifications won't work for the question asker from comments on an answer, unless the asker has made themselves notifiable through some interaction with that answer (see above link for what interactions qualify the user for notifications). In general, this means that if you want to notify the asker, then your comment needs to be on the question.
I can see how addressing this would be beneficial, but I'm not quite sure how to do it without possibly overwhelming askers with tons of new notifications.