If the passenger got on at Swindon, then they would be travelling with a valid ticket, as the off peak restriction only refers to London to Swindon I believe. I have broken return journeys taken in the off peak period at Swindon or Chippenham before travelling on the last bit of the journey on a train that left Paddington at a peak time.
According to restriction code YC, the one that applies here:
Not valid on trains timed to depart:
London Paddington after 04:29 and before 09:16 and after 16:40 until 18:36*
Reading after 04:29 and before 09:40 and after 17:10 and before 19:01
Slough after 04:29 and before 09:30
London Waterloo after 04:29 and before 08:15
Birmingham New Street after 04:29 and before 10:30
Not valid on trains timed to arrive at London Waterloo before 09:52.
* Off-Peak tickets valid on the 18:30 service for Kemble, Stroud, Stonehouse, Gloucester and Cheltenham Spa ONLY.
According to that wording the restriction applies to the train. So if you had an off peak ticket from Paddington to Bristol and broke your return jouney at Swndon, then as I read it that restriction would still prevent you from using that train for onward travel. Clearly you could use an off peak ticket from a station not mentioned in that restriction code for onward travel from Swindon, because code YC would not apply to that ticket
I agree with the main point you are making, and have made it to staff myself. Many peak hour services are now far less busy than similar off peak services.
I empathise with the sentiment expressed, but a peak categorisation applies to a time of day and not how many people happen to be on that particular train.
I agree that this is a matter that ought to be lookied into in more detail in the future if and when we know whether we will ever have a peak commuter period again, but that is not a matter over which we should make knee-jerk reacions at the present time.
In any case, the capability of the
DfT» to do anything quickly is much the same as for a dead sheep...