Discards existing ID3v2.4 data when set to ID3v2.3
When EasyTag 2.4.3's preference is to create ID3v2.3 tags, existing ID3v2.4 data is silently discarded/erased. It is not apparent to the user that this data ever existed, so they can easily erase it without realizing it while, eg., fixing a typo in in the song title.
The kind of data I'm talking about is what eyeD3 reports as these:
UserTextFrame: [Description: comment]
UserTextFrame: [Description: description]
Ideally, I'd like this data to be shown to the user even if it isn't editable in EasyTag, and I'd like a warning during save if it is going to be removed. Alternately, a warning dialog could shown when EasyTag opens the file, saying "This file contains additional metadata of a type unknown to EasyTag. It will be discarded if the file is saved."