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.

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 (__DEV__) {
          if (nextProp) {
            
            
            Object.freeze(nextProp);
          }
        }
        if (lastProp) {
          
          for (styleName in lastProp) {
            if (
              lastProp.hasOwnProperty(styleName) &&
              (!nextProp || !nextProp.hasOwnProperty(styleName))
            ) {
              if (!styleUpdates) {
                styleUpdates = {};
              }
              styleUpdates[styleName] = '';
            }
          }