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 (transaction instanceof ReactServerRenderingTransaction) {
    return;
  }
  var containerInfo = inst._hostContainerInfo;
  var isDocumentFragment = containerInfo._node &&
    containerInfo._node.nodeType === DOC_FRAGMENT_TYPE;
  var doc = isDocumentFragment
    ? containerInfo._node
    : containerInfo._ownerDocument;
  listenTo(registrationName, doc);
}
function inputPostMount() {
  var inst = this;
  ReactDOMInput.postMountWrapper(inst);
}
function textareaPostMount() {
  var inst = this;
  ReactDOMTextarea.postMountWrapper(inst);
}
function optionPostMount() {
  var inst = this;
  ReactDOMOption.postMountWrapper(inst);
}
var setAndValidateContentChildDev = emptyFunction;
if (__DEV__) {