The Sony is no different than any other eReader (I presume) if one embeds the fonts. That is, the fonts inside the ePub will be used instead of the stock fonts.
It works on all my eReaders.
My problem is that I embedded a
wrong font. I need to correct this, without recompiling the book (I'll lose some formatting and the hand-made TOC).
That is my problem in fewer words
.