This study investigates how students' commenting activities in online discussion forums relate to their motivation to learn, focusing on the quantity and perceived quality of comments. Conducted with seventy 12th-grade students in an AP English and Composition class, the research uses posts and comments from the youthvoices.net platform. The study finds that while the quantity of comments is linked to some motivational factors, the quality of comments is related to all four factors measured: sense of relatedness, perceived competence, interest-enjoyment, and value-usefulness. Insights on the traits of valuable comments are provided, offering guidance for improving online discussion structures to enhance student motivation.