Code review feedback

Author: rzikm

xml/System.Net/NetworkCredential.xml

@@ -80,7 +80,9 @@
  The <xref:System.Net.NetworkCredential> class is a base class that supplies credentials in password-based authentication schemes such as basic, digest, NTLM, and Kerberos. Classes that implement the <xref:System.Net.ICredentials> interface, such as the <xref:System.Net.CredentialCache> class, return <xref:System.Net.NetworkCredential> objects.
 
 > [!NOTE]
-> On Linux platforms, use of NTLM authentication may require installing the NTLM plugin for the GSSAPI layer used by the implemention. On Ubuntu distributions, the package is called `gss-ntlmssp`.
+> On Unix platforms, use of NTLM authentication may require installing the NTLM plugin for the GSSAPI layer used by the implemention. On Ubuntu distributions, the package is called `gss-ntlmssp`. Alternatively, applications may opt in for a managed implementation of NTLM by setting the `System.Net.Security.UseManagedNtlm` AppContext switch.
+>
+> On Windows, NTLM and Negotiate (Kerberos) authentication always depend on GSSAPI of the operating system.
         
  This class does not support public key-based authentication methods such as Secure Sockets Layer (SSL) client authentication.