Hmm- google says not:
http://www.robertdesprez.com/2013/05...-an-epub-file/
that article claims that cascading CSS will control how ADE behaves & hence how a sony reader would behave.
I suppose to test it properly I'd need to make a test book, just over a page long & then play with CSS value
I just opened lots of my already-read books in search of an actual example in a retail epub, but without finding one that had any explicit CSS, so maybe I've seen it only in books that were actually word or PDF conversions.