If you want to check if an IP has used by another person (I don't mean the whois-lookup), you have to use the IP Button in the topic. If a user has no posting, there is no way (to my knowledge) to check if another user registered from the same IP.
It would help a lot if you have such a checkup function in the ACP and/or the profile so that you can check the IP of users without any posts.
- (german community for bible & faith)
- the German support community for pbpBB