Sure you can. The other service will both let you add a comment and track what has been sent over. Of course, that's only if the service has been programmed f

Sure you can. The other service will both let you add a comment and track what has been sent over. Of course, that's only if the service has been programmed for it. G+ already is. G+ handles that on Google's side, and the other service would have to handle that on its side. Why would Google store stats for you about some competing service, when that service can do it just as well?