The author gives a teaching list of 51 Sunnahs of prayer.
• Deliberately leaving a Sunnah does not invalidate the prayer and does not by itself require Sujud al-Sahw.
• A person loses the completeness and reward attached to following the Sunnah.
• The commentary treats deliberate habitual neglect as blameworthy, but lighter than deliberately leaving a Wajib.
The next levels follow the author's list progressively.