When canvas chat is turned on, it was explained to me that by default it is enabled for all courses in the account. Below, I have explained reasons why Canvas Chat should be initially disabled by default for courses rather than enabled.
This is an all or nothing feature, so it's either on for your whole account or not.
Since it cannot be turned on for specific courses or sub-accounts, we would have to turn it on and give everyone access just so a few people can try it out and see how it works for our district. (There may be an option for some to use Chat in the Test environment, but not all districts/institutions have the test environment turned on.)
I was told by our CSM, "It will default to enabled once the feature is turned on at the account level, so you'll just want to be prepared to communicate that so instructors can turn it off."
We shouldn't have to tell teachers they have to turn it off right away. Our CSM also stated that expectations and procedures should be set ahead of time. Therefore, it is a good idea to turn Chat off when instructors are not present in the course so Chats don't get off topic and carried away with potentially inappropriate posts, especially in a K-12 situation. (Which I thought was very good advice.) If the suggestion is to initially turn Chat off when teachers are not present in the chat, it makes sense to have the chat disabled by default since at the time Chat is turned on for the account instructors may not be in their courses to turn Chat off right away.