A figure created in PowerPoint for Mac is pasted into a Microsoft Word for Mac document, but then a Windows based colleague with Adobe Pro and Word for Windows creates a PDF from the docx.

Problem: The figure is silently omitted (blank space on the page, no warning).

(a) BUG: even if you can't render it, doing so without warning is very poor as it means we need to check ALL the figures in a big report to make sure they have come out.
(b) PAIN POINT: there is no obvious vector format for the Mac user to use that doesn't get mangled in cross-platform use. (Maybe Microsoft's fault) and bitmap embedding has other issues.

The underlying image format is some kind of Mac embedded PDF, on Windows it says "Microsoft Office Graphic Object" with a low-res image thumbnail. But Microsoft Word's PDF export does at least use the low-res version.