Or, thank you for wasting your customers time attempting to figure out why one or more sites aren't responding appropriately on your network while they work on other networks.
Not everyone is clued into EDNS or why archive.is doesn't function with CF.
CF is wasting everyone's time.
And given it is the subnet number being sent, NOT the IP address that people here claim, the privacy concern is fairly low (CF knows your IP address in order to deliver the DNS answer back to you and archive.is knows your IP address when you request resources).
I'll take the performance improvement that EDNS client subnet can provide.