I am Evernote heavy user, and recently just notice if I type double dashes (–), it will automatically turned it into dash(-), if you are typing some linux command for note taking, typing double dashes (–) will turned into dash (-).
Apparently just found found out this is called Smart Dashes substitution. Here are the options can you turn if off on Evernote, or your Mac OSX.
Turning of Smart Dashes in Evernote
When you writing your note, right click and look for Substitutions > Smart Dashes, make sure it’s uncheck.
Turning Off Smart Dashes in Mac OSX
Alternatively, if you found the Smart Dashes / Smart Quotes are not useful for yourself, it can be turned off in Mac OSX.
Go to System Preferences > Keyboard > Text (tab) > Uncheck “Use smart quotes and dashes”