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.

if (typeof nextProp === 'string') {
        setTextContent(domElement, nextProp);
      } else if (typeof nextProp === 'number') {
        setTextContent(domElement, '' + nextProp);
      }
    } else if (propKey === SUPPRESS_CONTENT_EDITABLE_WARNING) {
      
    } else if (registrationNameModules.hasOwnProperty(propKey)) {
      if (nextProp) {
        ensureListeningTo(rootContainerElement, propKey);
      }
    } else if (isCustomComponentTag) {
      DOMPropertyOperations.setValueForAttribute(domElement, propKey, nextProp);
    } else if (
      DOMProperty.properties[propKey] || DOMProperty.isCustomAttribute(propKey)
    ) {
      
      
      
      if (nextProp != null) {
        DOMPropertyOperations.setValueForProperty(
          domElement,
          propKey,
          nextProp,
        );
      }
    }
  }
}
function updateDOMProperties(