After reading the whole dossier, nothing in there convinced me anyone's at risk here. Jazz didn't get his info spread around because Blockland "isn't safe," it all happened because of what he did wrong, so innocent people aren't going to end up in the same predicament that way.
As for being "hacked," you're no more likely to have your Blockland forums account stolen than you are to have any of your other accounts stolen. Keep a good password, don't give it out, and don't download anything weird. You'll be fine. I don't know the details of what the dll injector actually does, but I think the only thing it can do is allow people that downloaded it to cheat at the game, not compromise accounts. Unless you download the injector yourself, because for all I know it has a RAT or a keylogger in it or something, I wouldn't trust it.
If you don't do anything wrong and don't do anything stupid, you're probably perfectly safe.