anchor.diff:      return html;
     };
   
  -  var toolTip = function(tag) {
  +  const toolTip = (tag) => {
       if (inDiffMode()) {
         return 'Show diff ' + (tag-1) + '<->' + tag;
       } else {
  
positive.code: 
    // - - - - - - - - - - - - - - - - - - - - - - - -
  
    var makeDiffFilenames = function(diffs) {
      // align-right is for diff toggling added/deleted line counts
      return '' +
        '<table align="right">' +
  
negative.code:   // The [revert] button is available only from the review *dialog*.
    //---------------------------------------------------------------------
  
    let param = {
            id: "<%= @kata.id %>",
        avatar: "<%= @avatar.name %>",
        wasTag: "<%= @was_tag %>",
  