Rovo is telling me there is a setting that I can toggle on to allow customers to comment on other customers tickets within their portal
I can't find this setting?
You need to go to the Customer Experience settings (the portal configuration) rather than the project settings:
Click the Product Switcher (9 dots) in the top-left and select Service Management.
In the sidebar, click Customer experiences.
Select the experience linked to your project (likely named McCarthyCSMTest).
Click Customer access in the sidebar.
Find the setting: "Can customers comment on requests they can view?" and set it to Yes.