We got this from Ben, who has been in charge of taking this discussion forward:
Since the beginning of the year there has been a lot of discussion about recordings and what exactly they should be used for. After several meetings on IRC and a couple of huge topics on the style mailing list, we’re finally ready to bring in a new definition for recordings, and new style guidelines to go with it!
The new recording definition can be viewed at http://musicbrainz.org/doc/Recording
And the accompanying style guidelines are at http://musicbrainz.org/doc/Style/Recording
The new guideline brings significant changes to the way recordings should be used, so all editors dealing with recordings should take the time to read it.
As a short summary, recordings are now never produced solely through copying or mastering. This means that recordings shouldn’t distinguish between different masters of some audio – in general, a recording will correspond a particular mix or edit. In addition:
– AcoustIDs and ISRCs have been removed from the guideline – they are mostly irrelevant for managing recordings under the new definition.
– Guidelines for audio channels have been introduced.
– Existing guidelines have been expanded.
– Several in-depth examples have been added to explain how recording should be used.Also, as a result of these changes, the recording-recording remaster relationship type and the artist-recording master relationship type have been deprecated.
Thanks to everyone who was involved on mb-style and in the IRC meetings for your excellent ideas and contributions!
MetaBrainz Blog 
Just to be clear, this means for the moment at any rate that there is no longer a mechanism for marking a recording as a remaster. are we meant to mask tracks as remasters in some way or just not collate this info.
If an entire release is remastered by one engineer, then mark the new release as a remaster of the earlier release. If each track is mastered differently (eg. compilation album), add any info about the mastering to the annotation.
When there’s better support for masters, editors will be able store this information properly, most likely on some sort of master entity. Perhaps there’ll be more info on that after the development planning meetings next week 🙂
Could you please add examples to the style guidelines for japanese releases? Are this just different releases (from US/European albums) or how can I detect, if they are new recordings? What exactly makes the difference from an additional release to a new recording?
They’re normally the same recordings (well, except from any bonus tracks, which are obviously not in the originals 🙂 ). It’s very very unlikely to re-record the music for a Japanese edition, I’d say, and fairly unlikely to mix it differently; in the case it *was* re-recorded, I’d certainly expect it to be mentioned, and for a re-mix, well, if the sources say nothing like that, keeping them together sounds reasonable. They can always be split later if someone can prove otherwise.