Quote Originally Posted by mbncd View Post
I think that when (or just before) they implemented the merchantile houses, they said that while you were in them the game would recognise you as being in the city of the house you were in.
That's right. From Patch 1.22 Notes:

* While you are inside a mercantile house, your current location in player search will appear as the associated city-state. The same applies when you log out of the game while inside a mercantile house.

I even posted this same issue a few months ago and it seems I had misunderstood aforementioned information aswell. Still, anima costs for teleportations performed from the Mercantile House of the city-state you're currently at (i.e. Gridanian Mercantile House at Gridania) are wrong IIRC.