UPDATE: Mostly solved - see posts from 9/1 and 9/2.
ORIGINAL SUGGESTION: I know this issue was fixed in the recent Calibre update when it comes to downloading metadata to add and not overwrite. This would be AWESOME for regular editing of metadata where you can choose a bunch of books and add info to the comments of all of them without overwriting what is there. I currently have to go through each books and copy/paste to do this. It's a major library and takes way too much time!
He is the Calibre update info from the closed ticket for downloaded metadata for reference from release 1.26 on 2-28-2014:
"Metadata download: Add an option to merge the downloaded comments into existing comments, instead of overwriting (Preferences->Metadata download).
Closes tickets: 1285319"
The cherry on top would be to also be able to specify if edited comments (I'm focusing on the manual edits and not downloads) should be added to the beginning or end.
Example of use: editing a library where you have 20 or more books for the same author for whom you'd like to add a link to a specific website to the comments section, especially if you include the comments in book conversions and such.
