When i press the enter / return key on OS X 10.11 my lines of code are being duplicated rather than entering a new line in between the current cursor position.

I tried to modify the key bindings however it still didnt work. In order to do a proper enter for a line break I need to press shift+enter.

I also tried to use the same shift+enter key binding and still no luck.

Only happened after upgrading to El Capitan OS X 10.11

Fixed the solution by adding this to user key bindings

{ "keys": "enter"], "command": "insert", "args": {"characters": "\n"} }

]

Surely this is because you have installed some Sublime Text package that rebinds the enter key. It does not have anything to do with OSX 10.11 - I am using it myself without that problem.