This has been asked for, repeatedly. This observation over a year and a half to two years. It's not a priority, and the devs don't care.
Tournament chat is also screwed-up. (You can disable in the main tournament lobby, but, as soon as a game starts, you see the chat. You have to flip to the standings tab, which sill has movement during your game.)
For that matter, I just tried "Kid Mode" for the first time, and it sucks (balls). I understand the (all-or-nothing) considerations behind it, but, "isolating" kids from interacting -- especially in today's world (with the way things are going) -- I don't think is a good idea.
Thus, the solution is simply "Zen mode."
It's too bad that basic things like this are chalked-up-to a shrug of the shoulders, and/or a "we don't care" remark, and the all-or-nothing attitude. (But, hey, what can you do. This is the price of development, certain things get locked-in and are too time-consuming to fix later.)
Sorry about that last post, but, I'm going to let it stand. (I stand by my words. It's a sorry state of affairs that disabling chat via settings, or dealing with the tournament chat issue has to go on as long as it has.)