I would love to see the ability to toggle on and off being ported to, or atleast a pop up screen asking if it is okay for someone to port to you. I have too often been in a instance and have someone way too low for it port to me and making the situation more difficult then it needs to be. Please, make some sort of option to toggle off being ported or. Or make it so a pop up window asks if its okay for the person to teleport to you.
There are a few threads about this, at least that I have seen. I had a suggestion that next to the person's name in the friend list there could be a simple circle; if the circle was just an open circle then they are not in battle and you could port to them. If they are in battle then the circle would be closed in, that way you would know not to port without asking. I think something like this would eliminate losing a turn because of pop ups asking if so and so could port to you. Now, this wouldn't eliminate people coming to your house and reeking havoc, but at least this would help to eliminate unwanted porting into battles, bringing another bad guy and then fleeing.
Although now that I think about it, some people might STILL port even though the circle was closed just to be an annoyance, but my idea hadn't gotten that far yet.
But still, I think that this would be an easy way for KI to implement a way to know if someone was in battle without having to add too much stuff for the poor programmers to do :)