I know what you mean Bill.
I've seen many instances on many threads in many forums that go off topic. Some are innocent, but others not. I just figured it was the Nature of the Beast. I've caught myself doing it more than once. If I realize it, I delete my post and either PM them or start a new thread, but there are times I've not realized it and posted responses that should have been handled a different way.
As for notifying the staff, depending on what each individual considered to be an "Appropriate" response, this could end up a full time job editing thread responses. I've also seen many instances where other members pointed out when things went off topic and in some instances, the person deleted their response. Not always, but sometimes.
I would hope we, as members, can and should help police for this issue and notify the person(s) responsible if we think things are going Off Topic.