If you want to change a minor thing with a .tmLanguage and copy it to the User folder, delete everything except the things you want to edit and save it, you will have this language twice in the language selecting menu. This is very irritating. It would be good, if it would just work like with other settings files:
If something’s already defined, override it, otherwise add it. (Yes, it already works like this somehow, but the occurence two times says something’s weird.)

(Until we fleshed out the unofficial docs) check out packagecontrol.io/docs/customizing_packages. If you’re not using ST3, switch over.