Title is clear enough.
I run a very large forum, and I have alot of users that can read multiple langs. with no problems, they want to be able to see the original text without any translation, and not having to click down on it.
This is mainly for them in regard to PM's, not really in the threads themselves.
But sadly you can only control this via the whole board, it would be nice if the user could by himself decide via the user control panel, on how it wants to see his PM's displayed, etc.