First part is definitelly a bug, you cant spawn your own Trading post NPC when other player spawned it close to you, also you cant use thay NPC even if you own item for spawning it. Second is huge inconvenience for this price.
And yes the biggest problem about it that probably noone will do anything about that, I have found numerous redis posts and gw2 forum posts about it, and still noone done anything about that, even if we have already alot of other items that open window without spawning NPC...