I think users that have "View-only" rights must not be shown in assign/comment menu. It makes sense because they cant't answer to the comment and even change the entity (task/list...).
Often, for the security reason, I add some users-watchers to the task wich presence other active task users must not know.
From Clickup support:
Some teams uses "free Guest with view only rights" because they want the ability to assign tasks to many people without needing to be charged. If their guests need to do something in the task, then naturally the guest seat should count. However, if it's just a placeholding task for something somebody doing outside of ClickUp, then it can make sense.
But I think that for the such placeholding tasks in ClickUp must exist separate role, for example "Viewer" (it will cover all billing reasons).
And the users (Guests that may have "edit/comment/view.." rights) - are members of the workflow, and for the possibility to asssign them "can view" or "can edit" role Clickup users must be charged.