The biggest problem with a split forum is - IMHO - that a thread is created in one forum, but after a while the content drifts so far away from the original question/statement that the thread should be in another forum.

What should happen then?

Should the thread be moved?
No, because its start was in the correct forum!
Yes, because its end is in the wrong forum!

Should the thread be split?
No, because whichever spot you take to split it, some messages are out of context or unanswered.

Should the thread be duplicated?
No, because then discussion gets duplicated and/or harder to follow as you always have to look at two (or more if there are more than 2 forums) threads in different forums.

Just keep the forum as it is and simply ignore threads that do not interest you!

MudGuard