They likely employ a third party service to do extreme user finger printing. They'd tell you it is because of spam, but with their focus on being a highly sophisticated censorship and propaganda platform, they will find many areas of benefit. This can usually reliably grab uniquely identifying fingerprints about your browser and device, include supported fonts, supported SSL ciphers, and video card details. It's not worth trying to obfuscate and work around this, using a second device and a VPN seems the only way.