Communication needs to happen during active projects between Requesters and Workers for success of the project. In a current project (converted from issue queue), the ability to communicate in Updates is not available to requesters. Updates is not in the left navigation for Requesters when looking at an active project. I can't imagine Square is alone in needing the ability to communicate between Requesters and Workers throughout a project lifecycle.
I have already run into an issue of a Worker asking a question in Updates to a Requester and the Requester getting the email notification of the question but UNABLE to answer it.
Per customer service:
Currently, in Workfront a requester can only have view rights to a project. So they would be unable to make comments because they do not have contribute access. They will have contribute access to the issue and would be able to make comments.