We really should backport the fix that is in 1.0 to 0.9 for our international friends.
I can’t remember what the function was that had the problem but I believe it was
there may be others.
Unfortunately those functions are not pluggable but you could try replacing them from 1.0 into 0.9 and use SVN to handle upgrades which might work around it.
Made a note on TRAC https://trac.bbpress.org/ticket/1059