On the 15th October, Microsoft announced they will be updating the Microsoft Teams meeting options to allow an organiser to manager participants ability to chat prior to, during and after a meeting.
Once this update becomes available, meeting organisers will be able to go into the meeting options and set the “Allow meeting chat” setting to On, Off and During the meeting only.
For me, I love the ability to chat prior, during and post meeting with attendees, it stops users from turning to email for needless communication. This option will definitely come in handy though for those meetings where you only want discussion to happen during the meeting or if you are in education and you want to stop students using the chat option pre and post lesson.
This update should start roll-out in mid-November and be completed by the end of November. Check the Microsoft Roadmap here.