YEdit seems to set keybinding for toggle comment to 'CTRL-/' regardless of OS. This is right for Linux and Windows, but its not for Mac. On Mac the toggle-comment is typically bound to CMD-/ instead.
Should verify this bug is not already fixed in latest YEdit and report it there if it is not.
If/when it gets fixed we should adopt the fix and upgrade our YEdit bundle to latest. Or we can try and do some kind of workaround (e.g. changing the keybinding preference ourself).