There is always some idiot in the audience who will yell stupid things about the issue being a PC problem or a Macintosh problem ...
Without seeing the actual PowerPoint presentation file as well as the fonts involved, a definitive diagnosis cannot be provided. Having said that, instinct would suggest that the problem is associated with cross-platform differences in characters sets used by PowerPoint and/or differences in the fonts between the platforms. This is
exactly why using PowerPoint files as opposed to a PDF file (with all fonts embedded) created from the PowerPoint file for an actual presentation is not a particularly good idea.
One of the problems is that PowerPoint on Windows and PowerPoint on Macintosh handle fonts and character sets differently. PowerPoint on Windows has used Unicode encoding for a number of years; I believe that PowerPoint 2008 on the Macintosh is the first Mac version to support Unicode, at least for new documents.
- Dov Isaacs, former Adobe Principal Scientist (April 30, 1990 - May 30, 2021)
Well, using a PowerPoint file and fonts on the same computer the presentation was created on is relatively safe... it's when you move that file without the fonts that you start really asking for trouble.