It's certainly possible. There are plenty of people who have been assigned (usually small) subnets (e.g., a /28 or /29) and have their name, address, phone numb

It's certainly possible. There are plenty of people who have been assigned (usually small) subnets (e.g., a /28 or /29) and have their name, address, phone number, etc., publicly available via WHOIS. (For "residential customers", it was acceptable to not publish their personal details, however.) I'm not sure about the other RIRs but ARIN, at least, has (had?) a requirement that any assignment of a /29 or larger must be reported (see "SWIP" [0]). In other cases, a PTR RR for a single IP address could be enough to personally identify an individual. [0]: https://en.m.wikipedia.org/wiki/Shared_Whois_Project https://en.m.wikipedia.org/wiki/Shared_Whois_Project