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.

parentInfo = hostContainerInfo._ancestorInfo;
      }
      if (parentInfo) {
        
        
        validateDOMNesting(this._tag, null, this, parentInfo);
      }
      this._ancestorInfo = validateDOMNesting.updatedAncestorInfo(
        parentInfo,
        this._tag,
        this,
      );
    }
    var mountImage;
    var type = this._currentElement.type;
    if (transaction.useCreateElement) {
      var ownerDocument = hostContainerInfo._ownerDocument;
      var el;
      if (namespaceURI === DOMNamespaces.html) {
        if (this._tag === 'script') {
          
          
          var div = ownerDocument.createElement('div');
          div.innerHTML = `<${type}></${type}>`;
          el = div.removeChild(div.firstChild);
        } else if (props.is) {
          el = ownerDocument.createElement(type, props.is);
        } else {