Microsoft PowerPoint uses a different method of tracking changes a reviewer makes to a presentation. Only the sender of the presentation will see change markers.
Microsoft PowerPoint automatically resizes a font to fit text in a placeholder. You will have to apply the actual font size that the reviewer suggested in order to incorporate the text change.
I can't combine a reviewer's presentation with my original presentation.
You have either chosen to end the review of the original presentation, or you are trying to combine a reviewed presentation that was not created from your original presentation.
You designated the presentation you sent for review as a private document. Individual reviewer names will not be identified in your combined presentation.