When applying the HTML content differ (daisydiff) to Office presentation files converted to HTML (using the default office2html converter), the differences are not highlighted.
So for now we don't suggest the HTML content diff for Office presentation files, but only the text content diff that works well.
The blacklisted mime types are:
See ContentDiffHelper#getHtmlConversionBlackListedMimeTypes() for the complete list of blacklisted mime types.
We would like to find a good way to do this and activate the HTML content diff link for these files.