If you're seeing reserved Class E IP addresses (i.e., addresses in the
255.255.255.255 range) show up in your Account settings page for your Sessions or in Access Logs, then you're running into something called a Pseudo IPv4 address. This is a feature provided by Cloudflare to provide IPv6 compatibility with IPv4-only applications.
If an IPv6 request to Doppler comes through, Cloudflare will associate an IPv4 address pulled from the reserved Class E IP space with it. That IPv4 address is then what's passed on to the underlying application behind Cloudflare (i.e., Doppler). As a result, this IPv4 address will show up in Access Logs and your account Sessions list as your IP address.
In the future, we plan to disable this feature and display the IPv6 address in situations like this, but for now the pseudo IPv4 address will continue displaying.