I can guarantee you BadBear didn't base his feedback just off another member's, and it doesn't have to be just down to the same IP. If they both use exactly the same browser and operating system then that's good enough evidence in this case (and he may have other evidence I'm not aware of). Also, you're right that people sticking up for another isn't conclusive evidence alone but it certainly arouses suspicion, especially when they type the same way and use the same insults etc. More than a coincidence is it not?