[haertig]

Originally Posted by lumpynose

So if someone wanted to remove that, then they could open the opf file in calibre's editor and delete it?

It might be safer to overwrite it rather than remove it. So if the text string is, for example, 64 characters long (I didn't count it), then overwrite it with 64 random characters. The point being, not to make the entry any longer or shorter than it was originally, just make it different, but of the same length.

In this case (Amazon azw3 files) it may not make any difference. I don't know.
But generically, overwrites are safer than deletions when you don't know if the software that reads the data is looking for fixed structure sizes or not. It's never 100% safe to go messing with data when you don't know exactly how it is used/interpreted by the software. But it's usually safer to overwrite than to delete.