Originally Posted by kovidgoyal
The "override" is only for the display area. User defined column names are always prefixed by #, so they cannot override a built-in column name in any other context.
Curious. When I tried to name a custom column "Series" (I wanted a series column that didn't number the series), calibre slapped me on the wrist and said, "No, no, no!" How humiliating! (All seriousness aside, I got around it by naming the column " Series" with a space in front of the word; it displays close enough to the original to pass for it).