1) Can I chat another user's byteball address, or does the user have to send me a pairing code?
2) Can the pairing code be used by more than one person / address? Like, could I put a paring code in my sig line?
1. Only pairing code allows to pair and therefore to chat.
2. Sure. Otherwise we won't be able to pair with the exchange bot. There are 392 people there now.