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.

this._domID = 0;
    this._wrapperState = null;
    if (__DEV__) {
      setAndValidateContentChildDev.call(this, null);
    }
  },
  restoreControlledState: function() {
    switch (this._tag) {
      case 'input':
        ReactDOMInput.restoreControlledState(this);
        return;
      case 'textarea':
        ReactDOMTextarea.restoreControlledState(this);
        return;
      case 'select':
        ReactDOMSelect.restoreControlledState(this);
        return;
    }
  },
  getPublicInstance: function() {
    return getNode(this);
  },
};
Object.assign(
  ReactDOMComponent.prototype,
  ReactDOMComponent.Mixin,
  ReactMultiChild,
);
module.exports = ReactDOMComponent;