Well they threatened to delete my account and close my own wiki if I did anything about it so I just didn't.
Technically yes, you can revert the damage done to wikis. However, in the final instance of "Novazoid's attacks" the wiki took several days to revert as the code had been screwed up severely. You can modify the site's URL to reveal several instances where code important to the wiki layout is visible and you can go there and mess it up. If done enough times to different lines of code you can pretty much screw up the entire place. The code often has lots of dashes in it, and they can be configured to anyone's liking unless the page is protected.
This is why some wikis look different than others, as users edited the code to make everything seem different from other wikis.
I will be returning to Wikia itself sometime in August, 2015, but the blackmailer on the other hand will not be returning as far as I know. If you want me to explain further about the entire blackmail scenario I could.