This would be really useful to have. Just hash the IP; instant privacy.
EDIT:
I guess it wouldn’t be quite that simple, a hash would need to use a private and non-predictable salt for each IP to prevent someone from generating a lookup table.
EDIT 2:
An API endpoint would work great; one that gives a list of the last 5 or so IPs (obfuscated) an account used, and the number of logins on each IP (or number of messages sent, or some other benchmark). That would take care of the issue of seeing whether or not that’s the main IP they log in with, or just temporary IP, like somebody else’s internet connection. And if it listed the number of accounts that logged in from that IP, it would help gauge whether it’s a public IP (like a university) or a private home connection. In fact, Twitch could pre-cache the owners of all the major IP blocks, which should make it pretty easy to differentiate between private connections from an ISP, and commercial connections, which it could include as a flag in the API response. Just thinking out loud here, since I think it’s a good idea.