There are two ways of doing this; you can opt to change the direction globally or you can choose to have a button override it on an edit page. These two options have been there for quite some time, they have been essential for us to support right to left oriented languages.
Nikerabbit added a new gadget the other day; they allow us to change the text area font style. There are three three styles: monospaced, sans and serif. In a previous blog post I mentioned that Firefox was broken for the Lingala wikipedi. This is actually not the case; the problem is that monospaced fonts have been selected for Firefox and this is what makes Firefox, Safari and Opera break.
Monospaced fonts do not support characters like "ɔ́" properly, but the sans and serif fonts work as they should in most modern browsers.. Internet Explorer is broken because it does show the wrong characters, Chrome is broken because it does not show a character.