There’s nothing wrong on inviting your friend through referral but having same IP address and some sort of similarities in the account pattern .....
When was it announced that several users from this gangster group were using the same IP address? I think I missed that somewhere.
Like the comment part you snipped said, I also personally believe that using the same IP address on several account shouldn't be much of a problem since there are several gamblers who make us of the cyber Cafe, where they offer internet access to several computers though or with the same ip address - so in this sense, account operational pattern is what should matter, and then also, to prove that one have no link what so ever with other accounts that are accessed from the same computer, such user should be able and ready to verify his or her identity when the casino request it.