This pilot study aims at integrating a socio-pragmatic concept, Cooperative Principles, into an experimental writing project on the genres of comparison and contrast. It reports on a six-week study of five undergraduates voluntarily recruited in a university located in central Taiwan. In surveying their writing momentum before and after the installments of relevant knowledge needed for these genres of English writing, the researchers conformed to the qualitative paradigm, collecting the Pretest and Post-test writing products, distributing B2- and C1-leveled CEFR self-assessment questionnaires over the first and last class sessions, conducting a self-reflection questionnaire survey at the last session, and keeping a reflexive journal to trace the learning momentum of each of the five participants. The instructional process was not entirely lecture-oriented; the participants were encouraged and guided to construct knowledge in each of the class-based activities. With content analysis and constant comparative method, the results indicated two primary facets of issues essential for teaching the genres of comparison and contrast in a L2 writing setting. In addition, constructs for teaching such writing genres were pointed out, and learners' momentum was transparently manifested by means of the established CEFR can-do statements. Other pedagogical suggestions were also included in this study and they were anticipated to inform future practitioners of diversified aspects in teaching the comparison and contrast genres linguistically, semantically, and pragmatically.