You CAN UN-Brick a Nook Tablet…
I bricked my Nook Tablet (8gb) just a few days after I got it. It would only boot via an SDCard. Without a bootable SDCard, the screen would remain totally BLACK. I had tried (I think) every suggested solution on XDA and a few other forums. All without ANY success.
But TODAY, I was able to restore the Nook to stock configuration. I will be writing more articles about the Nook now that I can do something with it (grin).
For a full step-by-step guide, see the article How To UN-Brick a Nook It includes a video of the process (takes less than 5 minutes!