Aiming to investigate the polarization between Science and Conspiracy (BESSI et al, 2016) - an increasingly relevant issue when considering the growth of the internet as a space for collaborative learning - a qualitative-interpretative analysis (DENZIN; LINCOLN, 2005) is performed on the comments section of the video Fomos à Lua? from the YouTube channel Nerdologia. To that end, a socio-semiotic perspective of language (HALLIDAY; MATHIESSEN, 2014; MARTIN, 2016) is adopted, with the theoretical contribution of Systemic-Functional Linguistics, using the Appraisal System (MARTIN; WHITE, 2005; TAVARES, 2014; VIAN JR, 2012). In this perspective, the principles of writing-in-interaction (BULLA, 2014) are considered, understanding that computer-mediated communication (CMC) reconfigures aspects of face-to-face interaction in writing. The methodology adopted is document analysis (TAVARES, 2014), as it favors the observation of relevant factors in the maturation process of individuals and societies (APPOLINÁRIO, 2009 apud SOBRINHO, 2015). Results suggest that polarization creates Imagined Communities (ANDERSON, 2008; HARJU, 2016), human groups characterized by the lack of a criterion for their communion, which is based not necessarily on a social bond but on the belief (imaginary) of such a bond. This fragile criterion of communion may cause the members of an Imagined Community to polarize their discussions, using the resources of Engagement and Graduation (MARTIN; WHITE, 2005; WHITE, 2015) to limit opposing positions and to potentiate their own. It is proposed that the use of evaluative resources demonstrates two affordances of such communities: solidarity in group maintenance and cynicism in conflict resolution. The way Imagined Communities operate highlights what appears to be the inherent conflict in the use of YouTube for scientific dissemination, since it is defined at the same time as both a collaborative on-line learning platform (FINARDI; PORCINO, 2014) and as an affinity group (BARTON; LEE, 2013).