Hashed IPs can be brute forced fairly easily (by calculating the hash of all 2^32 IPs and finding the one that matches the relevant hash in the database). Maybe there isn’t much difference between storing a real IP, and a hashed IP?
But what if a secret salt is included in the hash? And the secret salt is forgotten & replaced with a new secret salt each month? Then old IP hashes from within the same month, could still be compared with each other. Let’s say some accounts were created a few years ago (edit: or months ago), and now suddenly become active and start misbehaving. Then one can see if they likely belong to the same person, and lookup even more accounts by that person, by looking up the ip hash. But, since the salt was forgotten, it would no longer be possible to “reverse” it and find the real IP. Both privacy and a bit security, at the same time.
(Probably not a good idea to do now, because would be complicated. But maybe good to have in mind … if starting to think about this again … some years later)