$.support.cors
does return true
in IE 11, as demonstrated by this fiddle:
X-UA-Compatible
set to IE=9
disables cors support.
The following will output "true" in IE 11
<!DOCTYPE html>
<html>
<body>
</body>
<script src="https://code.jquery.com/jquery-1.9.1.min.js" type="text/javascript"></script>
<script type="text/javascript">
$(function() {
$('<h1>').text($.support.cors).appendTo($('body'));
});
</script>
</html>
But with <meta http-equiv="X-UA-Compatible" content="IE=9">
will output "false"
<!DOCTYPE html>
<html>
<head>
<meta http-equiv="X-UA-Compatible" content="IE=9"></meta>
</head>
<body>
</body>
<script src="https://code.jquery.com/jquery-1.9.1.min.js" type="text/javascript"></script>
<script type="text/javascript">
$(function() {
$('<h1>').text($.support.cors).appendTo($('body'));
});
</script>
</html>