A conversation server hosts a conversation having a plurality of participants, the conversation server enables a first client to display at least a portion of a conversation to a first participant. The conversation server receives a notification the portion of the conversation was viewed by the first participant at a first time while in a first state. After receiving a notification that the portion of the conversation has ceased to be viewed by the first participant, the conversation is edited to a second state at a second time. At a third time that is after the second time, the conversation server sends, to the first client, information enabling the first client to display a markup of the portion of the conversation that is indicative of one or more edits that transition the portion of the conversation from the first state to the second state.