I submitted this in-game, but thought I'd throw it to the wolves too.
Linguists (and bards and maybe con artists) should be able to change their accent at will.
There's plenty of thread about accents. Just look around. 'Nough said here.
Here are a few links that might help.
http://www.zalanthas.org/phpBB2/viewtopic.php?t=11837
http://www.zalanthas.org/phpBB2/viewtopic.php?t=6976
http://www.zalanthas.org/phpBB2/viewtopic.php?t=4447