Here's the skinny on this "issue":
When someone notices a thread is obviously posted in a sub-forum where the OP is unlikely to get a correct/helpful answer (I didn't say "wrong sub-forum"), a site team member can operate the site's "Move Thread" software and tell the system where to move the thread. Not only does the software move the thread, it automatically sends the OP a PM similar to this:
"
Thread moved (Leprechaun low point drains)
{OP},
I wanted to let you know that your thread,
Leprechaun low point drains, has been moved from the
Berkshire forum to the
Coachmen Motorhomes forum.
Even though it has been moved
I’ve left a redirect notice (Permanent) in the original forum so other users can find the thread."
The site team member doing the move doesn't have to/is unable to alter the contents of that PM. Notice the sentence/phrase in
green. The site doesn't want interested parties including to OP to 'lose' the thread. This 'redirect' allows any member to get to the thread from either sub-forum for a period of time although the thread practically lives only in the 'moved to' sub-forum.
After this explanation sits here a while, I will move all these "Coachmen thread in the Berkshire sub-forum" posts into the Forum Admin sub-forum.