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.

case 'input':
    case 'select':
    case 'textarea':
      inst._wrapperState.listeners = [
        ReactBrowserEventEmitter.trapBubbledEvent(
          'topInvalid',
          'invalid',
          node,
        ),
      ];
      break;
    case 'details':
      inst._wrapperState.listeners = [
        ReactBrowserEventEmitter.trapBubbledEvent('topToggle', 'toggle', node),
      ];
      break;
  }
}
function postUpdateSelectWrapper() {
  ReactDOMSelect.postUpdateWrapper(this);
}
var omittedCloseTags = {
  area: true,
  base: true,
  br: true,
  col: true,
  embed: true,
  hr: true,
  img: true,
  input: true,