This tool provides live feedback about the technical quality of a glyph. The goal is to help new type designers get through the "Beziers Are Frustrating!" phase a little more quickly. Keep in mind that the displayed notes and marks are generated by math and are not a definitive list of things that must be corrected. It's always (okay, not always) acceptable to break the rules as long as you have a good reason. Think of the comments as reminders to think through why you have things where they are.