http://y5wnzw4e6i7srm2gqadlow5anhlaj5avdkzbwzbmrxwkygxdp7ffieqd.onion/blog/noticer-noticing-ipv6.html
Thinking more about it, if Mr. Hacker Man connects to a lot of random routers... they all have to get their IPv6 address from the ISP so the ISP could determine stuff about the device if they wanted to, maybe, I don't know, I do not know anything about assigning IP addresses*).