What happens if at some point in the future the forum is hacked and someone releases the user logons and IP addresses?
This is why everyone should have a punting email address.
The IPs only your ISP could do something with this. And I doubt they'd respond to a request from Lucious Lynda wanting to sue a member as she used to be called Paul.
Your ISP would only release your details if the police asked them to. And even then not freely.
So you'd have to rely upon, 1. someone hacking this site. Then releasing the IP address online.
2. Then this prostitute finding this (most prostitutes wouldn't even know where to look).
3. Then them asking your ISP to release your information to them, and them doing this.
4. Then taking this to court and the court actually listening to this claim (which they won't unless it was very sinister someone had done, and if it was the case they'd get banned from her for doing that sinister thing anyway).