MB version 2.5.5804
Observed Issue:
When importing mp3's with <COMMENT SONGS-DB_CUSTOM#> (#'s being 1-5) and/or <INVOLVED PEOPLE> tags, MB does not read them into its database. I thought it might have been due to the fact that the tagfields had a space " ". However, MB successfully read in <MUSICBRAINZ ALBUM ID>, a tag with two spaces.
Steps:
1) Preferences > Tags (1) > Define New Tags
2) Add in COMMENT SONGS-DB_CUSTOM1, INVOLVED PEOPLE, or MUSICBRAINZ ALBUM ID under the id3 column and give it the appropriate identifier.
3) Save
4) Under custom tags in the Tags (1) page menu, add in display name of choice next to "custom 1: " and select the identifier (set in step 2) to "save to music file as tag."
5) Apply and save
6) MB rescans the library in an attempt to read those custom tags into its database.
Expected result: After MB finishes scanning and updating the mp3s, one should be able to see the appropriate values for the custom tags in the mp3's edit menu (Shift+Enter) under the "Tag (2)" tab.