FWIW, as someone who's not contributing to lyx at all right now, let me come
down on the side of opposing red dots except when absolutely necessary.
Each thing you add to LyX makes it that much more confusing for new users,
in addition to becoming more cluttered for experienced users.
For language, as opposed to font changes, I guess you might want to have
some GUI stuff. (Since it's much more rare for most users, it'll be less
confusing.) If you're only going to have two languages, tehre are several
possibilities, like having a different background color or something. For
RTL/LTR the most logical thing to me seems to be something like
|
<-|->
|
ALternatively, you could change the cursor depending on the direction.
-Amir