A Unity ID allows you to buy and/or subscribe to Unity products and services, shop in the Asset Store and participate in the Unity community.
Separate names with a comma.
Way too much stuff breaks???? Like what? Unity? How does Qt, or Visual Studio (a Microsoft product), or Xamarin, or XCode, or any web server...
So it's 2017, OSX has had case sensitive file systems since before Unity was even considered, and Linux/Unix have had case sensitive file systems...