Here's a thread where this question was asked and responded with a simple 'no.'
In some other LMS communication tools, this is possible. In transitioning users from one LMS to Canvas, they look for features like this and I'm hoping that others agree that this should be optional; either at course or institution level.
Why would this be beneficial? Having the ability to cc the help desk on a thread to loop them in? Simply writing to another instructor in your department that's not in the course to ask a question without searching for a joint course that you all might be loaded in? Just sharing and collaborating in general. Any other thoughts?
Is there another tool that could be integrated to facilitate this better than the default Canvas conversation tool?