I have seen one or two forums that run like that. But I was under the impression it was the moderators who decided when a thread should finish & when the topic was starting to deviate from the original question(s) & thus split it off into another thread. (I think they also had a rating system. Or perhaps that was another forum, where points were awarded for interesting & relevant threads & answers. I'm not sure I especially liked the concept or the way it came across as a visitor. But then I haven't been involved with it so I don't know how well it works & how annoying that might be to some people.)

But I see your point & an interesting & relevant one. It could certainly be helpful to members. But then again, there's too many members who just jump in & post a new thread without searching their topic for answers, or looking at the stickies which already have 80+% of most popular questions answered, or reading the forum rules. It is no exageration that over 90% of questions asked on the forum from day to day have been asked before.