Taking into consideration that this is one of the most popular and useful plugins for MB that definitely expands its functionality so that it's much better for tagging than any other music player or manager is, IMHO the issue should be handled somehow before the 2.1 stable release.
The easiest way I could think would be to add an information window to MB that would pop up when "Preferences--> Layout (1) --> Configure Fields" is launched. I think 2 or 3 sentences with a description or warning (even if available in English only) would be enough to prevent such bugs and make users more convenient with the plugin and MB itself.
A more fundamental change could be applied if needed for the 2.2 version or newer.
I can't imagine this could be done better with the plugin update as it's a MB 'fault'.
We should take advantage of discovering the bug before the stable release.
Steven, boroda - what do you think