It's very bad form (and against the rules) to make chat the focus. You will eventually get reported if you do it a lot. A short chat at the end is fine.

The session template is: brief greeting > outline what you're gonna do > wish the other person well > mute mics and get stuff done for the bulk of the session > end of session chime sounds > share how well you did (and here you can chat for 2-4 mins if both parties are keen)

So far it has not happened to me. You only speak before starting and at the end. During the session we both mute our microphones.