Is it true that shutting down my PC with the USB Drive still plugged in may harm either my PC or the USB drive?
The drive will almost certainly be fine, and so will your computer. The problem of corrupting a drive almost always comes from removing it without clicking the "eject" or "safely remove drive" feature on your operating system.When the operating system is trying to write data to a drive, it actually "queues" the write operation because it can't happen instantly. If the write operation is interrupted, you will end up with a portion of the drive's space marked as filled with data, with no apparent way to delete the data, which is commonly referred to as the "corruption" on your drive. If you shut down your computer properly, the operating system should tell the write operations in the queue to stop, or it will wait until it is finished.I once made the mistake or removing an SD card in the middle of an enormous write operation, and a huge chunk of the space was marked as used, but I couldnt delete it. I ended up needing to reformat the card, and then it worked fine.TL;DR) Almost surely nothing to worry about, as long as you shut down properly. The operating system should implicitly "eject" the USB drive for you.