Most likely, if on leaving the platform and getting a ticket check you were to think quickly, and say "oh, sorry, I wasnt feeling well, had to get off, and now Im just looking for the toilet" you could get away with it.
Yes if someone was feeling unwell, I do not see how the TOC could deny them access to fresh air/medical attention etc. However it is unclear how ill you'd need to be to justify that, and what steps they could do to check. Answers to that would be interesting but probably won't be forthcoming.
Also, if you admitted a mistake, and apologised to the conductor, and took out your wallet offering to pay the extra necessary fare, you would also get away with it.
As I said in the other topic, if you are admitting a mistake, it's a penalty fare (where PFs apply). If you admit that it is deliberate, then potentially they could prosecute, but I feel this would be risky for the TOC, and TOCs tend to only prosecute where they can be sure of getting a conviction (before anyone says "How do you know?" my source for this is a poster by EC saying they have been successful in all cases. I know EC have not existed for very long and are not the same company as SWT, but they probably work on a similar basis.
Ill bet you any money that when being challenged on the platform, this couple started shouting and swearing at the staff. Or possibly let slip that their car was parked right there, giving away the fact that they had planned their scam all along......
We really cannot possibly infer that at all. RPIs who are looking to catch people out, will do just that, to any law-abiding person, they do not just go after people who start shouting and swearing. And if they had let out it was a 'scam all along' then that is a misuse of a PF, surely, as if it really was against the rules and was deliberate then that's an MG11 not a PF. Unless, of course, the TOC is scared of not winning the case. But if the TOC is so sure it's against the rules and if the person had admitted it, what would they be afraid of?