Problem is, some limits are hard to detect until you've exceeded them; "listen to your body" really must be augmented by details and rigor around safe progressions through the practice (which, to complicate things, obviously vary by individual).
Also, there are some limits that should not be exceeded, period. Like the cases in the article where they exceeded the operating tolerances of the neck and gave themselves strokes.
Yoga certifications really ought to include a basic anatomy and physiology component.
