[justaj]

I'm just wondering how Reddit managed to do that. Do VPN companies have to register their endpoints in some kind of a VPN database so that Reddit can flag them as IP addresses coming from VPN companies? How otherwise would Reddit know that a particular IP address belongs to a VPN company?

[panic_canine]

You could infer if there were a lot of activity or a lot of disparate activity from a single IP address that it belonged to a VPN.

[justaj]

Doesn't this go out of the windows with IPv6?