Should the transcription or photo reverse notes not also be contained in the image metadata where they belong?
You know, that's a good question and I don't know the answer.
I usually put document transcriptions in two places and sometimes three. The two basic places are into a fact note in RM and into a source/citation note for that fact in RM. As a source/citation note, the transcriptions follow all the citations around, not just the fact basic fact note for the data. For example, I have a birth certificate fact and a death certificate fact, etc. The initial citation goes with that fact, and then is memorized and pasted to related facts such as birth and death themselves. The third place is that sometimes I create a TXT file with the transcription and the TXT file is in the same folder and with the same name except for the file extension as the image file itself.
In the case of photos, I tend to make a second copy of the image in a lossless file format (usually PNG), expand it with white space at the bottom, and annotate the photo in the white space. Unless the image file is some sort of layered format, this annotation just becomes pixels and is not really text anymore. This technique is sort of like writing on the back of a photo that's printed on paper except it prints on the "front" of the photo - in the added white space at the bottom.
For whatever reason, I have not done the same sort of annotation with image files of documents as I do with photos, so my document transcriptions are somewhat separated from the document itself. Another place to store the the transcriptions would be in formally defined metadata fields that are defined for many types of image files. My concern here is that such metadata fields tend to be poorly supported by software that displays and edits image files, and therefore the metadata can be totally invisible to the user and can easily be lost. I'm not familiar with any of the annotation tools mentioned in this thread, and they may address some of my concerns about the image metadata being invisible and/or lost.