title_body: Are soft hyphens supported by epub devices?
upvoted_answer: I don't have definitive information here. But a google search reveals that Kindle has improved their support for soft-hyphens recently. But mostly this is done within the reading system. 
  
  https://groups.google.com/forum/#!topic/standardebooks/v_oRXH6mLwQ
  https://www.mobileread.com/forums/showthread.php?t=285812
  
  Quote: 
  
  
    While Amazon, intent on keeping developers miserable, declined to explain how their new hyphenation engine works, it actually appears to just be support for the Unicode soft hyphen character (U+00AD).  If Kindle encounters a soft hyphen near a line break, it considers it a hyphenation opportunity.
  
  
  I did a quick check of Google Play Books and Kindle for Android and see that body hyphenation doesn't seem to be turned on. I seem to remember that iBooks hyphenated body text (maybe). The Amazon formatting guidelines doesn't mention anything about it. 
  
  I suspect that unless you are using specialized or technical texts with a lot of long multi-syllable words, it doesn't make sense for the author/publisher to add the soft-hyphen character yourself.