Even with debugging disabled in the backend the error message that debugging is not supported was still popping up in IE9. I assume this message should only show if you have debugging enabled.
alert("Unfortunately console object is undefined or is not supported in your browser, debugging wp-ajaxify-comments is disabled! Please use Firebug, Google Chrome or Internet Explorer 9 or above with enabled Developer Tools (F12) for debugging wp-ajaxify-comments.");