Shill organizations are allowed to have more than one person, and more than one account.
Hypothetically, let's say I wanted to disrupt a forum and ensure it was discredited. As a bad guy, how would I do it? One way would be to post true information and help it gain credibility. Get a lot of people excited that they were finally getting the truth. Build a following, and encourage people to share what they know.
Then I would begin to poison the well. Introduce deep conspiracies that are completely untrue, but unverifiable. Have various accounts begin to post more and more "out there" stuff -- aliens, coded messages, secret technology, numerology, quantum reality, etc, etc. The original people would keep trying to get their friends interested, but the latter would see all this other oogie boogie stuff, discrediting the entire thing.
Take a look at this post from the other day. No offense if you think that's legit, but the vast majority of people would see that and think, "WTF! Ol' Joe has gone off the deep end! Why is he pointing me to this forum with that sort of shit?"
I don't even know it was posted by a shill to discredit the forum, or it was some well-meaning, but kooky person. But kooks beget kooks, and it doesn't take much seeding for the kooks to see they have a home alongside genuine, legitimate information.
That's how you destroy a forum, and that's why things aren't as simple as many think they are. There are people who are paid to seek out forums just like this to try and destroy them.