I'm not sure how or if you could implement this. Take a look at the Share permissions matrix. Removing comment ability and visibility from such a role would go against the conventional use case for the collaborator role - someone who can upload a new version but not see comments?
I suspect you would have to implement it at a node level using a behaviour. Either way, this is not a trivial task.
Digital Community Manager, Alfresco Software. Problem solved? Click Accept as Solution!