The only documentation I've seen is another post by Stefan. This is apparently a part of East Asian Language support but the keyboard shortcut is active in Word. It works in Word 2003 and later but not Word 97. In some ways I can see why it is not documented. As Paul said earlier, for virtually anything you want someone to read, it is probably not appropriate.

But, as you pointed out, for a title it can be useful.

I have been working on and off on a chapter about aligning text in Word. It is not finished, but I have added reference to distributed text here.