From Mavericks theMAC OS X embedded default text editor tool, the TextEdit uses autocorrection by default so replaces your correct characters to funny ones.
This is getting more funny when you open and edit a JSON file for example. And you won’t realize what went wrong a quite long time 🙂
So, just switch it off:
Apple symbol > System preferences… > Keyboard > Text > Uncheck “Use smart quotes and dashes”
TextEdit > Preferences… > Uncheck “smart quotes” and “smart dashes”
In TextEdit, Edit > Substitutions > Uncheck “Smart Quotes” and “Smart Dashes”