Information line for moved threads.
This comes up occasionally, when threads get moved around - what is reasonable discussion in the original forum for a thread, then looks argumentative or disrespectful after a thread is moved. This leads to more discussion of the perceived insult or disrespect rather than the original point of the thread.
So... what I'd suggest, is that if a thread is moved from one forum to another by a mod or staff, that something like a "system message" post be inserted which says "This thread moved from Forum A to Forum Z". Maybe even at the top of the page as a thin bar in addition to at the point of the change, because we know that people reply without reading all the way to the end first.
If the point of moving a thread is to put it someplace for more targeted discussion it would be helpful to keep that discussion on target rather than the current state which often just leads to more discussion of what is now off-topic for the forum it's been moved to. The "system message" posts would just let everyone know that it was moved so that folks can relax their sensitivities a bit.