[lozenge]

What would that look like?

"You have opened your Word 97 document in Office 2003. The quirks have been removed, so it might look different now. Check every page before saving as docx."

"You have pasted from a Word 97 document into an Office 2003 OOXML document. Some things will not work."

[ranger_danger]

If you want a look at how this (doesn't) work in practice, just look at Libreoffice. I once made 3 hours worth of comments on a Word doc, and as soon as I saved it, they all vanished into thin air.

And for the pedantic, yes it warns you when saving as a .docx that "not all features are supported", but it does that every time, for every document, so nobody pays attention to it or has any idea what it even means. To me the way it handles this is just completely unacceptable.

[mjevans]

Office could freely continue to support their old proprietary formats if they wanted.

In an ideal world a converter would generate E.G. a 1200 PPI render of each page, then compare it to a similar render as provided in the nearest rendition in the allowed simple new format. Those could be diffed to produce a highlight of areas that changed.

The software could then ask if the transcription from one format to the other was close enough, or if there were some corner case that wasn't good enough.

Bonus points, collect feedback if the end user is willing to submit examples.