comment (depth 0)
  comment (depth 1)
    comment (depth 2)

{{#messages}}
      {>message}
    {{/messages}}
    <!-- {{>message}} -->
    <div class="{{getClasses()}}"">{{text}}</div>
      {{incrDepth()}}

      {{#comments}}
        {{>message}}
      {{/comments}}

      {{decrDepth()}}
    <!-- {{/message}} -->

{
  data: {
    incrDepth: function () {
      this.depth++;
    },

    decrDepth: function () {
      this.depth--;
    },

    getClasses: function () {
      return 'depth' + this.depth;
    }
  }
}