It has been common to use video records of instruction in teacher professional development, but participants have rarely been encouraged to evaluate teachers and students' actions in those records, allegedly because evaluation deters from the development of a professional discourse. In this study, we inspected teachers' online discussions of animations of classroom episodes realized with cartoon characters, looking at the difference in the content of conversation turns when members made evaluative comments and when they did not make evaluative comments. We were interested in finding out whether making evaluative comments correlated with participants' reflection on their professional practice and proposal of alternative teaching actions; for that purpose we used systemic functional linguistics (SFL) to develop a coding scheme that attended to evaluation, alternatives, and reflection in forum discussions. We found statistically significant evidence that the more the participants actively evaluated the teaching in the animations, the more they proposed alternative teaching actions and reflected on instructional practice. We relate these findings to the notion of social presence in online discussions.