Each chat room has their own message boards called tiles, in which friends can have a deeper discussion on only the topics they are interested in.
If you do not want to chat with strangers then you can disable private messages, and block them.
Choose what you want to talk about by switching chat rooms to change topics to suit your mood.
Tiles do not delete automatically like conversations in the chat room, or in instant messaging.
You can also enable private messages only from friends, so only users in your friend’s list can text you.