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.

validatePropertiesInDevelopment(tag, nextRawProps);
    }
    var updatePayload: null | Array<any> = null;
    var lastProps: Object;
    var nextProps: Object;
    switch (tag) {
      case 'input':
        lastProps = ReactDOMFiberInput.getHostProps(domElement, lastRawProps);
        nextProps = ReactDOMFiberInput.getHostProps(domElement, nextRawProps);
        updatePayload = [];
        break;
      case 'option':
        lastProps = ReactDOMFiberOption.getHostProps(domElement, lastRawProps);
        nextProps = ReactDOMFiberOption.getHostProps(domElement, nextRawProps);
        updatePayload = [];
        break;
      case 'select':
        lastProps = ReactDOMFiberSelect.getHostProps(domElement, lastRawProps);
        nextProps = ReactDOMFiberSelect.getHostProps(domElement, nextRawProps);
        updatePayload = [];
        break;
      case 'textarea':
        lastProps = ReactDOMFiberTextarea.getHostProps(
          domElement,
          lastRawProps,
        );