Expand on server behavior

draft-ietf-httpbis-optimistic-upgrade.md

@@ -97,7 +97,7 @@ A version number of "2.0" corresponds to HTTP/2.  Every HTTP/2 connection begins
 
 ## "TLS"
 
-The "TLS" family of Upgrade Tokens was defined in {{?RFC2817}}, which correctly highlights the possibility of the server rejecting the upgrade. If a client ignores this possibility and sends TLS data optimistically, the result cannot be valid HTTP/1.1: the first octet of a TLS connection must be 22 (ContentType.handshake), but this is not an allowed character in an HTTP/1.1 method.
+The "TLS" family of Upgrade Tokens was defined in {{?RFC2817}}, which correctly highlights the possibility of the server rejecting the upgrade. If a client ignores this possibility and sends TLS data optimistically, the result cannot be valid HTTP/1.1: the first octet of a TLS connection must be 22 (ContentType.handshake), but this is not an allowed character in an HTTP/1.1 method.  A compliant HTTP/1.1 server will treat this as a parsing error and close the connection without processing further requests.
 
 ## "WebSocket"/"websocket"