A method for facilitating document review includes obtaining data indicative of an ordered relationship among electronic communication documents in a conversation thread group and one or more missing electronic communication documents. The method also includes causing a visualization of the conversation thread group to be presented to a user via a graphical user interface of a client device, in part by causing one or more graphic elements, corresponding to the missing electronic communication document(s), to be displayed at respective positions along axes of the visualization with a particular visual coding that is reserved for missing electronic communication documents.