Hi. Let me summarize.
1. On the Firefox rendering engine.
Firefox (and probably thunderbird) uses an original rendering engine.
Ok, that explains the peculiarities.
2. Firefox vowel marks and fonts.
For many fonts, firefox disconnects Arabic letters at vowel marks.
Only exceptional free fonts which are shown correctly I know are
* mry_KacstQurn and DejaVu *.
Ok, this is the point where our problem occurs. DejaVu does *not* work for some additional characters like for Kurdish and, as I understand heer, Malay.
# expect improvements for it. There may be a chance for 3.0 which
# branches deeply.
Thanks for the clarification. Looks like we have to wait for firefox 3 to get some things fixed.
Oh, from firefox-1.5, bidi properties for text input area can be set.
http://www.k2.dion.ne.jp/~oibane/aonl/en/browser.htm