Shaky, I can see why you might make this request. And it is a challenge on message boards like this one world wide.
But, I offer a different perspective on the matter.
On rugby and soccer boards in Europe, there is a sometimes fiercely moderated commitment to keeping all of the discussions of 1 theme in one thread. IMO, that leads to something worse than a sprawl of discussions in various places.
There are threads in, say, Leicester Tigers forums that last over YEARS. The first post might be entitled "Manu Tuilagi." The thread, with perhaps 400 posts, might cover years of issues relating to his emergence as a young player, his international success, his injuries, his getting in trouble, his fitness for a match, etc. etc. Finding anything in such a thread is virtually impossible.
So, the commitment to keep posts on a theme centered in one thread has its own problems. Obviously, the above is an extreme. But I question the idea of trying to confine 1 theme to 1 thread.
The question is, what is the theme? People see different nuances on a theme. Are all posts about Fisher and Kroenke the same? I don't think so. I think a poster can legitimately think, "Hang on, there's an angle on this issue that is being lost. I want to stress X ..." And the poster starts a new thread.
Is that a legitimately new angle? That depends on one's perspective. But it can also be related to thread hijacking. A poster may feel that a thread on a topic has gone off on a tangent and wish to pull it back. Starting new threads or contributing to existing ones is a form of the poster dialoguing with the discussion.
Personally, I'd suggest letting posters follow their instincts. Well, them's my two cents.