Support communication using keybase

in the great Bisq software there is a message function in the tickets. Now I have an open ticket and according to mediator I have to contact him via keybase.
What are the reasons for continuing the communication via keybase? I have to leave an email address and the TradeIds. Here I spread trade information by an additional way. Must that be?
If this is absolutely necessary: what information is sent to the stored email address? I would reserve the right to deposit a one-time email address.