I have a really simple font family with Regular, Bold + Italics
I’ve set up the style linking as I always do and everything works in InDesign and textedit. When I try in Word/Powerpoint the BoldItalic doesn’t work at all, it always turns into a faux italic.
Is this on Word for Mac? If so, I experienced the same. It is apparently a bug in Word, nothing in the font can be done to prevent it (except not style-linking the fonts). I reported it some months ago already, but MS has not fixed it yet.