This seems to be a regression. While in a text area, choosing any option from the 'Writing Direction' context menu does nothing in WebKit ToT. Shipping Safari does align text to whatever is selected, however, the alignment is reset as soon as you click outside the area. I'm using Safari 2.0.4 and Nightly 16296.
Created attachment 10519 [details] Test Case
*** Bug 11081 has been marked as a duplicate of this bug. ***
Fixed in <http://trac.webkit.org/changeset/34896>.