The link above says it's for creating links in EPUB books to use different fonts saved on the Sony. I don't believe it works for LRFs. For LRFs, you have an option in Calibre (well, I assume it's still there in 0.6, I can't get it to work right on my computer) to IMBED the font in the LRF file.
The results are hit-and-miss per font. So, I could get it to work for Georgia font, but not for Verdana. The only way I know to test it is to create one and open it in the Reader. The file will be larger than normal by about the size of the font, but there's no guarantee the Sony will read it with the embedded font (that was my experience, anyway).