Autodecode?

[JN via Digitalmars-d-learn]

Related to this thread: 
https://forum.dlang.org/post/xtjzhkvszdiwvrmry...@forum.dlang.org

I don't want to hijack it with my newbie questions. What is 
autodecode and why is it such a big deal? From what I've seen 
it's related to handling Unicode characters? And D has the wrong 
defaults?