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.

styleUpdates = styleUpdates || {};
            styleUpdates[styleName] = '';
          }
        }
      } else if (registrationNameModules.hasOwnProperty(propKey)) {
        
      } else if (isCustomComponent(this._tag, lastProps)) {
        if (!RESERVED_PROPS.hasOwnProperty(propKey)) {
          DOMPropertyOperations.deleteValueForAttribute(getNode(this), propKey);
        }
      } else if (
        DOMProperty.properties[propKey] ||
        DOMProperty.isCustomAttribute(propKey)
      ) {
        DOMPropertyOperations.deleteValueForProperty(getNode(this), propKey);
      }
    }
    for (propKey in nextProps) {
      var nextProp = nextProps[propKey];
      var lastProp = lastProps != null ? lastProps[propKey] : undefined;
      if (
        !nextProps.hasOwnProperty(propKey) ||
        nextProp === lastProp ||
        (nextProp == null && lastProp == null)
      ) {
        continue;
      }
      if (propKey === STYLE) {
        if (nextProp) {
          if (__DEV__) {