So you want to limit the ability of those to speak their mind on a board designed to allow people to speak their mind? If you limit the number of threads started by people you have no idea how much it might stunt the growth of the forum. There are a lot of people on this forum that post in threads but never start threads.
Now if you have a problem with threads being about the same topic or in the wrong forum, report them. I do. Once I had some threads moved or closed I decided it was time to follow the rules the best I could, BUT I also decided it was time to make sure others did as well. If a thread is a like to other's report them to get merged. If it is in the wrong forum, report it to get moved to the right one. Now something I did learn recently, is if tow threads are a like, but one is in Zone 2 and the other is in the flamezone, they can't be merged because the threads follow different rules.
Now as far as your complaint and idea of limiting posters to starting threads, no, and it is mostly because you don't agree with their view point. As far as accusing people of being sock accounts, you need to have better proof than what you just came up with. And are sock accounts illegal here? Can one person have two accounts?