Python will turn your everyday binary strings into Unicode strings when necessary. But things get trickier if you put non-ASCII characters in Byte strings.

via. http://lobstertech.com/python_unicode.html

The ebook reader in linux was written in python and chokes on a lot of abnormal characters and I think the above is the reason why.  This could be a problem with the nook and other ebook readers but I’m not sure and it’s really not a priority to find out.   I know the nook will not accept an epub with a malformed stylesheet.css even though the python linux e-reader will.

It will be interesting to find out how some of the bigger tablets handle this.