Just yesterday, we read Team Geek, by 2 famous Google engineers. When they were developing Subversion, they had a similar problem. In their email list, they found that just one participant was using up 70% of the core project contributors' responses. They concluded that their "energy and focus were being sucked away"(on page 98 of the book.) by this single participant.
They were discussing technical details of an open source version control system. The percentage of population who can and will join such a discussion, is severely limited. Imagine who and how many will join if we discuss such general topics like, "Goals of National Education," "Meaning of Life" etc.
Parkinson(of Parkinson Law's fame) had to say this: Whether to open a 5-million-dollar plant can be decided in 5 minutes. The decision as to whether to open a 500-dollar canteen or bicycle shack needs far, far more time, simply because there will be more participants.
Team Geek/Subversion's solutions:
1. email that person, asking him to stop
2. phone that person, asking him to stop
It was then, now is many years later. And they were not Forum business. Developers in Forum business can do better.
I am very encouraged by the following advances: Vanilla identifies bad people and keeps them out
and Gamification drives user reputation and abilities.
Our Solution 1
You're right if you decide not go full AI. Still you can use NLTK or other tool kits. You can word-count, check themes/sentiments behind forum posts, group/cluster posts similar in tone or content, and so on.
Our Solution 2
You can check who are posting most, most frequently. You can alert moderators or other users to check the quality of such participants' contributions.
You can stall or ban such participants.
Our Solution 3
At least, you can tweak your user interface to crowd some posts while elevating some posts at the same time, and you can do it randomly. Sigh.