Pretty sure it was only somewhat recently with the 2.8.x/25.xx releases.

@JKnott It is unusual, but it's the standard Comcast setup when you have a business account with static public IPs. For residential, or lower-tier business accounts, you get a dynamic public IP. I'm talking about v4, but they are now providing a static v6 block with the v4, and a residential user gets a dynamic /60.