Yep, I know you can.
You can multi-client in Felucca just the same as Trammel, but in Felucca, there is a chance for the players themselves to stop it happening if they have an issue with it. So the way I see it, a. you are paying for 2 accounts and playing them, so whilst you may be able to do content easier than a solo player could, you are also taking a risk, and something could be done about it if necessary.
I've raided spawns where someone is multi-clienting, and they have to make a choice as to which character they save, and which dies.
If you get the game at a quiet time where no-one picks up on you, fine.
For me, it is the fact player justice is physically able to intervene and you would be taking that risk, hence it is all ok.
In Trammel, it is a far more grey area, because everything is just risk free in this sense. If a player had a problem with your activity, he could not do anything about it.