If a session has been created in a shared workspace, then all members of the workspace by default have viewer rights to that session, and therefore the ability to search and use content from the session.
This is different than being specifically invited to collaborate on a session. If you’ve been invited to collaborate (as either an editor or viewer) then you’ll receive emails about comments on the session. However, if a user simply has access to the session as they’re a workspace member, then they won’t receive these emails. Learn more about workspaces in our knowledge articles about the Workspaces overview.