The comma's not technically a keyboard shortcut; it's a database delineation key stroke, very commonly used for this purpose. It works in other database places in FCP.
I agree with the OP; I think it's a bug in the localization.
Not sure what's going on. It's working for me as well. I tested it this morning because things change, and it worked. Now it's not working anywhere. Of course I did switch to test other languages, and since then it's gone.