Hello Ali,
yes, I think phpBB supports all ltr languages by default.
@callum: I want it in the core, too. Please talk with the devs, not with me. Before I will do patches I want to know if the features will be included to the core. Then I'm a MOD author and a co-developer, too.
@all: I thought about it again. There is no need for two engines. The data is stored in ltr to the database. I'm quite sure this can not been changed. So two engines are not possible to realize.
So just you have to create an extra BBCode bar. And the second thing is a feature which translates the BBCode tags for the texboxes (textareas) for posting and editing.
Bye Martin