Yep and even better than that; most if not all residential ISPs use Carrier-grade NAT so one IP (which changes), now represents hundreds if not tens of thousands of their customers.
At the very best, you could maybe narrow an IP to a very vague geographical area like several suburbs, or a specific town maybe.
Sorry but, 4chan account? There's no such thing as that.
Not denying that Muskrat did this, but there's no such thing as an account on that site.