Lines 1654 to 1676 in the mapps.html. The alert window allows the user to know that writing a review has been disabled.

mapps.html

    function submitReviewDialog()
    {
        // We're done with getting the review
        hideReviewDialog();

        // Submit the comment
        /*dojo.xhrPost({
            url: "proxy.ashx?http://www.arcgis.com/sharing/content/items/" + currentDetailsId + "/addComment",
            headers: {"Content-Type": "application/x-www-form-urlencoded; charset=UTF-8"},
            postData:
                "f=json&comment=" + encodeURIComponent(dijit.byId("reviewDialogText").value),
            handleAs: "json",
            timeout: 60000,  // ms
            load: function(data) {
                // Update the reviews
                updateReviewsList(currentDetailsId);
            },
            error: function(text) {
                alert(text);
            }
        }); */
        alert("Writing a review have been disabled");
    }