An electronic device with a display and a touch-sensitive surface stores a document having primary content, supplementary content, and user-generated content. The device displays a representation of the document in a segmented user interface on the display. Primary content of the document is displayed in a first segment of the segmented user interface and supplementary content of the document is concurrently displayed in a second segment of the segmented user interface distinct from the first segment. The device receives a request to view user-generated content of the document. In response to the request, the device maintains display of the previously displayed primary content, ceases to display at least a portion of the previously displayed supplementary content, and displays user-generated content of the document in a third segment of the segmented user interface distinct from the first segment and the second segment.