Moving a thread between forums kind of keeps a copy of it

I moved this thread from the development forum:

but as you see in the image (and in the developer forum), it's still listed in the old forum. Is this a feature or a bug?

Brandon.ConnectIQ 5 days ago

I was wondering the same thing, because I noticed this as well but haven't had time to look into it. I may be remembering something from another forum platform, but I remember at one point being able to specify whether the thread should be retained in its original forum for a certain period of time. I'll see what I can figure out.