For what it's worth, I had the issue as well in IE11:
<!DOCTYPE html>
and IE=Edge
settings mentioned in the question<head>
elementAfter a while, I found out that:
HTTP Header:
User-Agent: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 10.0; WOW64; Trident/7.0; .NET4.0C; .NET4.0E)
but
JavaScript:
window.navigator.userAgent === 'Mozilla/5.0 (Windows NT 10.0; WOW64; Trident/7.0; .NET4.0C; .NET4.0E; rv:11.0) like Gecko'
So I ended up doing the check on the client side.
And BTW, meanwhile, checking the user agent is no longer recommended. See https://developer.mozilla.org/en-US/docs/Web/HTTP/Browser_detection_using_the_user_agent (but there might be a good case)