To me it doesn't matter so much, as I am clicking the "new post" button, but I think some only reads what is going on in general discussion. I used to do so myself for a long time, until I discovered the aforementioned button, so if a discussion happens in an obscure forum instead of in general discussion it is like you put a damp cloth on the discussion, because you limit the discussion to those who specifically goes to the obscure forum. And if someone doesn't give an input for a long time it won't show up in the new post list either.
I thought you said you were only going to move threads which hadn't been active for some time. Looking at the threads it seems like most where active very recently. How about having duplicate threads? One that is running in general discussion, and one that is saved for posterity in alt. Right forum?