It probably is a subject for a thread of its own, as the issue of verbal authority to travel reappears consistently in many of these threads about disputes.
Firstly, I am in no doubt that you are absolutely correct about those who are intending to dodge fares and also about people hearing want they want to, but that is part of the problem with verbal authority. When even the advice given in the penalty fare guidelines refers to "a person [who] appears to be acting for or on behalf of a train Operator ... has indicated travel is allowed", you can understand why (perhaps incorrect) advice is acted on by an honest customer who has no intention of fare dodging.
I know you doubt whether the person who spoke to Adam_ was a Northern staff member and you may be right. We can neither prove or disprove Adam_'s account. But I recently went to a Northern staffed station to buy a ticket from the ticket office and I was told they couldn't issue the ticket (Northern Explorer 55 day ticket) from their system. I was further told that as the on-train conductor's machine was a different system they may be able to issue the ticket, so I should board the train, failing that, try again at the station where I was due to change trains, where the booking office was operated by Virgin (different system again, apparently) Clearly this would involve me boarding a train and travelling without a ticket with only verbal authority to travel. But would I be believed if I followed that advice, because ostensibly I would be doing exactly what Adam_ did.
Please Mr Railwayman, what should I, as an honest customer, do?