XMP files have an issue, which is that there is no established file extension or naming standard for anything for proprietary RAWs (e.g., ARW, NEF).
For those files, the XMP is the raw file name with .xmp. Simple. But JPEG, DNG, etc. don’t follow that rule. That’s because of R+J pairs. If you shoot ARW + JPEG, then there are two original files and one XMP. Adobe could have specified what to do there, but instead they decided to punt and write the metadata into the original files.
There is obvious risk to modifying original files, and some people are dead-set against modification just on principle (understandably).
Nitro’s current solution is to write XMP for JPEG, DNG, etc. using the format
Unfortunately, no other app uses the convention, so the XMP files are not seen by those apps.
There are only two solutions: 1) use .xmp for those files (which won’t work for any R+J pairs), or 2) write into the original.
My plan is eventually to offer both but not be happy about it 🙂