You can find all predefined and user defined shortcuts under
Preferences > Key Bindings - Default
Preferences > Key Bindings - User
When you need to add a shortcut or change one which defined in Default just copy related line to Key Bindings - User
also check Json syntax which sublime uses for configurations. I haven't any idea what changes in french canadian keyboard but I hope it would solves your problem.
Independent from keyboard, Sublime says :
⌘ + / Comment/un-comment current line
⌘ + ⌥ + / Block comment current selection
Updated :
Default Shortcut List : http://docs.sublimetext.info/en/latest/reference/keyboard_shortcuts_osx.html