As I have leveled up I have learned to ask before porting, in case someone is in battle and doesn't want another enemy brought in. I have also learned to ask people on my friends list to show me the same respect, if they don't pick up the habit on their own.
One thing I can't do, though, is communicate about this with my friends who have menu chat only. Not only are they unable to ask me before porting, they are unable to see me or other people doing this in order to learn about it. My own kids understand the reason for asking first, but are prevented from doing so by the lack of appropriate phrases on the chat menu.
Could we please have some things added to the chat menu (especially during battle, when it is most often a problem) such as:
Can I port to you now? Please ask before porting! Stay and fight!
And these existing menu chat items are needed during battle:
Wait a minute Stop that Please go away
This won't eliminate unannounced porting, but there are a lot of menu chat players out there who could and would learn to play in a less self-centered way if only they are given the necessary tools and examples. There might even be a few more text chatters who would find they can enjoy having a considerate menu chatter for a friend.