When using Picard with mp3 files and id3v2 version 2.3 tagging configured, the "Work and Movement" plugin writes MVIN and MVNM tags even though these are not valid tags for id3v2.3.  If id3v2.3 tagging is selected, these tags should be written as some form of TXXX tags.

Granted this is probably mostly the fault of the "Work and Movement" plugin, but at a minimum Picard should not allow invalid tags to be written, and preferably they should be converted to a TXXX tag (like other tags that are not valid in id3v2.3).