I've read many threads regarding the removal of the [PDOC] tag and I always come away scratching my head. I have never altered the settings in Calibre (other than selecting output device) and my converted books
always display on the bookshelf,
never in documents. I have never removed the [PDOC] tag and have Kindle DX selected as the output device.
It's curious that I seem to be the only one with no problem with the tag in place.