spelling & clarification
Some of these 'metadata' are not 'regular' in the way they are stored, comparing them would be a fair amount of additional code work.
Also note that some of the 'metadata' would be difficult to compare because they are not stored in the XML files, but rather in the Gramps initialization files.
====Note regarding older backup files====
In the past Gramps allowed data to be input in ways that are no longer allowed. When you import an older backup file, many of these issues are silently corrected for you. For example, Gramps used to allow leading and trailing spaces in name fields. Gramps now removes the leading and trailing white space when the data is entered.
The Database Differences Report performs it's work by creating a temporary Database and importing the backup file that you specified. A side effect of this is that if your Gramps Database has been around for a long time, it may still contain things that are not currently allowed. But the comparison will be done against the backup file that has all of those issues fixed. Each has the potential of showing up as a difference, but on examination they look the same. It is quite hard to see those leading/
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