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.

if (internalInstance) {
    var owner = internalInstance._currentElement._owner || null;
    if (owner) {
      var name = owner.getName();
      if (name) {
        return '\n\nThis DOM node was rendered by `' + name + '`.';
      }
    }
  }
  return '';
}
/**
 * @param {object} component
 * @param {?object} props
 */
function assertValidProps(component, props) {