We need a return to WYSIWYG principles. Any metadata stored in a file should be shown to the user in some way, to make them aware of that metadata existing. And if the metadata is incomprehensible to the user, then maybe it shouldn't be stored at all. There shouldn't be any surprises. If a file has an embedded thumbnail preview of itself which could become out of sync with the main image data, both should be shown to the user so they have an opportunity to notice it.
That's a bit of a weird use of WYSIWYG, which is usually used to mean that you can't see the metadata. For example, imagine you're editing a WYSIWYG document and enter:
A
Ctrl+I
Enter
Ctrl+I
B
This will look like:
A
B
If you later start typing on that intermediate line, though, your text will be in italics. This is what users expect, and is in contrast to outting a little "italics" markup symbol on the line, as people did pre-WYSIWYG or do today in Markdown, HTML, and other markup languages.
