When sending questions in a project to a guest user, there should be an option to prevent the guest from making any changes in the answer and be able to only add comments. This is basically like a view permission and edit permission.
This is so that the guest's inputs are vetted before it goes into the answer. Or else, the guest could spoil the current answer (if there was already an answer made by an inside user).
This was suggested by a customer in ticket TKT-211381.