I was just soloing toward the end of a t2 run, and went to invite a friend who was in Haven. I accidentally chose the Join option, and was ported back to town.
1. There should be a confirmation dialog for every single effing thing in the game. FFFFUUUUUUUUU-
2. Why is there even an option to join a friend in town? It should be grayed out in this case.
1. I sorta support. At least reasonable things, I don't want to confirm again that I wanna buy something from Basil...
2. Makes meeting up easier. If you are in different havens or the clockworks, you can join and you'll appear right beside your buddy without having to say "meet me at Arcade Haven 5". You will appear right beside him without having to worry about that.
Another use of that is quick trading, maybe you have a friend that has an item for you waiting and you're in the clockworks. You can join him in Haven. Pick up your item, switch to that weapon, and rejoin your party (assuming you are friends/guildmates with them).