Wikipedia, the online encyclopedia, is a trusted source of knowledge for millions of individuals worldwide. As everyone can start a new article, it is often necessary to decide whether certain entries meet the standards for inclusion set forth by the community. These decisions (which are known as “Article for Deletion”, or AfD) are taken by groups of editors in a deliberative fashion, and are known for displaying a number of common biases associated to group decision making. Here, we present an analysis of 1,967,768 AfD discussions between 2005 and 2018. We perform a signed network analysis to capture the dynamics of agreement and disagreement among editors. We measure the preference of each editor for voting toward either inclusion or deletion. We further describe the evolution of individual editors and their voting preferences over time, finding four major opinion groups. Finally, we develop a predictive model of discussion outcomes based on latent factors. Our results shed light on an important, yet overlooked, aspect of curation dynamics in peer production communities, and could inform the design of improved processes of collective deliberation on the web.