Apple - How to disable smart quotes

In addition to System Preferences, this feature can be turned on and off in each app via Edit > Substitutions. Make sure you check that setting as well.

In El Capitan (i.e. 10.11.1), I solved it by changing the Smart Quote settings:

1. Open Keyboard in System Preferences
2. Go to Text tab
3. Change values for "for Double Quotes" and "for Single Quotes" from drop-down selection to use the simple quotes "" rather than ““

That's it. No need to disable or do any other workaround. Hope this helps, as I had this problem with Message app when posting code.

This shell script disables smart quotes in all applications that currently have preferences files:

for d in $(defaults domains|tr -d ,);do
  osascript -e "app id \"$d\""&>/dev/null||continue
  defaults write $d SmartQuotes -bool false
  # defaults write $d SmartDashes -bool false
  # defaults write $d SmartLinks -bool false
  # defaults write $d SmartCopyPaste -bool false
  # defaults write $d TextReplacement -bool false
  # defaults write $d CheckSpellingWhileTyping -bool false
done

Uncomment the commented out lines to also disable other substitutions or spell checking.