When you interact with a NPC from a distance, you run up and go to a default location. Some of these default locations are really inconvenient. I am thinking especially about the 2 leather NPCs in the LW shop in EC - if you talk to the Skinning trainer, your toon will occupy the same location as the LW trainer, and vice-versa with talking to the LW trainer making you take the same location as the Skinning trainer.
This is incredibly annoying because when you try to interact with the trainer when someone is standing there (through no fault of their own), the default selection is the player. Double-click selects the player, if you aren't watching closely and open a trade window, it will be with the player (I find random people opening trade windows on me a little disturbing), not the vendor. Having to click the arrow buttons on the pop-up is an extra step which requires paying attention and alertness - not something I am always up to when I am doing my dailies (I often do dailies at times when I am too tired to actually play content).
Solution: Change the default interaction position for the NPC's in question.
I am sure there are other places where this happens, I will update this thread when I come across them. Other players might chime in also with places they find where this happens.