If we ever "lose user account data" and ask you to sign up again (or remove account functionality entirely), then you should not trust this site any longer.
If this were to happen (extremely unlikely), then this site would now be an FBI honeypot.
You would also likely start to see "mods" (not us) encouraging all to post violence.
I believe you can trust this site for as long as your user accounts work, which will hopefully be forever.
Keep in mind that to verify whether your user accounts do work, you also need to check whether an incorrect password doesn't work.
A single hashed IP and nothing else. Hashed email address if provided.
Just a point of interest. What is the reason for the hashed IP. I guess that way you could confirm someone came from an IP, but you wouldn't be able to provide the IP if asked. I assume the IP is individually salted. I guess the underlie reason to do this, is so you can block an abusive IP. Just questioning out loud. Not expecting an answer.