Pardon the double-post.
A blacklist by, say, 30 people in 10 minutes probably means you did something wrong. And anyway, it's not a guillotine, it would just lock the account for review, and could easily be undone. If it turns out, after review, that the mass reporting was just users working in concert to be jerks to one player, then they themselves could face the banning that RMT would get after a conclusive investigation.
By the way, such investigations would be greatly facilitated by the automatic report/blacklist button that has been suggested by countless users. It would be hard to abuse an RMT report button that copypastes text automatically. Frankly, I don't think most people who just want to be mean to another player would even bother using such a system for such an inevitably failed endeavor.
To that point, is there any evidence of people using the existing system to do that to people? All I'm talking about is making something that already exists easier to do. If there is no known concern about people abusing the reporting system that way now, I don't think there is any reason to believe that making it easier to use would open the floodgates. If there is evidence of such activity, my next question would be: is there evidence that that is going on more than RMT SPAM is? Because there is an awful lot of evidence of the latter going on. If they're both abuses of SE's rules, then why not implement the framework that addresses the one that is taking place on a far larger scale? It seems like it would make everyone's life easier.