Ludwig Do I understand right that you are talking about sidecar XMP files? Tonfotos can read those too, but it always prefers built-in XMP, if it exists. And current version never writes to sidecar, it only writes into built-in XMP inside JPEG.
Sidecars are the thing when you are dealing with some rare formats, such as different flavours of RAW. In that case it is preferrable to write into sidecar, rather than supporting each and every version of RAW files, which are dozens. However, when it comes to very standartized and popular formats like JPEG, PNG, TIFF, etc. - using sidecar is really strange aproach. Pretty much every software out there can read built-in XMP from those.
