As part of "attic create", being able to specify a message that later gets displayed with "attic info" would be useful. For example: attic create --comment "some comment" ...

Sometimes there is information that you want to include about a backup (archive event), which is too complicated to use in the name of the archive itself. This might be multiple lines of text.

Or maybe being able to change the comment at a later point in time, without changing the fingerprint of the archive or the the name of the archive. For example, you want to put a comment on an archive that "this was taken back when X was working" after the fact.