Just if you want to still use the comment tag:
Apparently Windows considers the language settings for "comment" which have to be the same for the mp3 tag and the explorer comment field.
/t/7632/1
shows how to adapt the mp3tag default comment language setting.
As this is a method that only works on your local machine and for one language, most tags on the other hand are the treated equally regardless of the OS language, I would prefer to use the tags (just like you did now).
BUT: as MP3tag has so many functions to manipulate even such specialities, you may want to write a little action that sets the correct language for your comments