The increasing use of social media to share knowledge in medical education has led to concerns about the professionalism of online medical learners and physicians. However, there is a lack of research on the behavior of professionals within open online discussions. In 2013, the Academic Life in Emergency Medicine website (ALiEM.com) launched a series of moderated online case discussions that provided an opportunity to explore the relationship between anonymity and professionalism. Comments from 12 case discussions conducted over a one-year period were analyzed using modified scales of anonymity and professionalism derived by Kilner and Hoadley. Descriptive statistics and Spearman calculations were conducted for the professionalism score, anonymity score, and level of participation. No correlation was found between professionalism and anonymity scores (rho = -0.004, p = 0.97). However, the number of comments (rho = 0.35, p < 0.01) and number of cases contributed to (rho = 0.26, p < 0.05) correlated positively with clear identification. Our results differed from previous literature, the majority of which found anonymity associated with unprofessionalism. We believe that this may be a result of the fostering of a professional environment through the use of a website with a positive reputation, the modelling of respectful behaviour by the moderators, the norms of the broader online community, and the pre-specified objectives for each discussion.