I have this problem too! I have numerous non-OS fonts installed, and I created custom XML styles so that they could be set as the body and header fonts in my word files. Now, some font aren't displaying properly (i.e., Word is slanting the font when it has
an italic otf available), and some word isn't even displaying at all.
I have also noticed that word is ignoring some font facilities, and treating each otf file as a separate family. For example, what was once simply Lingua Franca (with roman, italic, bold, and bold-italic) in the font menu is now four entries consisting of:
Lingua Franca-Roman, Lingua Franca-Italic, Lingua-Franca-Bold, Lingua Franca-Bold-Italic.
This problem is especially irritating considering that some of these fonts I paid money for, and which can no longer be used in word—I am instead forced to revert to using Pages, or some other word processor.