Preserving a sub tag of "comment:" won't work. E.g. "comment:iTunNORM". Other sub groups like "performer:guest" work. "comment:" works too.
The actual issue was that it didn't work for tags with uppercase characters in them: https://github.com/musicbrainz/picard/commit/4cbc0e149eebe49acf9ad12dfbd2df3f7fb5c4b4
Bug
Closed
Normal
Preserve tag won't work on comment: sub tags
The actual issue was that it didn't work for tags with uppercase characters in them:
https://github.com/musicbrainz/picard/commit/4cbc0e149eebe49acf9ad12dfbd2df3f7fb5c4b4