In Sublime Text 2 it was possible to comment out a line or a block of lines with Ctrl+/ and Ctrl+Shift+/. According t
On OSX Yosemite, I fixed this by going System Preferences, Keyboard, then Shortcuts. Under App Shortcuts, disable Show Help menu which was bound to CMD+SHIFT+7.
System Preferences
Keyboard
Shortcuts
App Shortcuts
Show Help menu
My keyboard layout is Norwegian, with English as the OS language.