The 'comments' attribute is not modifiable

One specific role seems to get this error, where the comment box disappears, one user managed to copy and paste into the field, but received the error "The 'comments' attribute is not modifiable". I have checked the permissions for the role, and appears they should be able to add a comment based on permissions, and nothing in "Preconditions & Follow-up Actions" appears to be blocking the adding of a comment either, so I'm not sure what the issue is... weirder still, if I give myself the role, the discussion disappears for me as well, even with my other roles as the same.