Thank you PHil,

I'll submit the bug report as you suggest, although I'm not sure if they'll be bothered to fix it any time in the near future.

I'll suggest that they contact you for validation purposes, I'm sure some vendors might warm to the idea of someone who knows what they're talking about, others can be quite arrogant though. Still it's always worth a try I say.

Whilst on the subject, thinking about what you've been saying about copying out xmp-crs, I'm wondering if it's worth the effort of reworking the idea of keeping keyword edits AND raw data using only the XMP block copying when writing to the image.
I presume there's nothing wrong with the idea of (for example), creating a sidecar from LR then one from Acdsee and using Exiftools to copy the keywords from the latter to the former. Then block XMP copy the result back into the image?

One other question: What would be the advantages of MIE files as opposed to xmp sidecar files. Is there a significant reason to use one against the other?