This usually means that the user mixed up our lowercase/uppercase naming convention; see https://github.com/facebook/react/pull/3429#issuecomment-85166440.

We could add a message like

> Warning: The tag <commentBox> is unrecognized in this browser. If you meant to render a React component, start its name with an uppercase letter.

We'd check this only once per tag and only in development mode.

payload: styleUpdates,
        });
      }
      CSSPropertyOperations.setValueForStyles(
        getNode(this),
        styleUpdates,
        this,
      );
    }
  },
  /**
   * Reconciles the children with the various properties that affect the
   * children content.
   *
   * @param {object} lastProps
   * @param {object} nextProps
   * @param {ReactReconcileTransaction} transaction
   * @param {object} context
   */
  _updateDOMChildren: function(lastProps, nextProps, transaction, context) {
    var lastContent = CONTENT_TYPES[typeof lastProps.children]
      ? lastProps.children
      : null;
    var nextContent = CONTENT_TYPES[typeof nextProps.children]
      ? nextProps.children
      : null;
    var lastHtml = lastProps.dangerouslySetInnerHTML &&
      lastProps.dangerouslySetInnerHTML.__html;
    var nextHtml = nextProps.dangerouslySetInnerHTML &&
      nextProps.dangerouslySetInnerHTML.__html;