The problem with "I'm sorry SuperVoyager but this simply isn't the case! Please actually research before you post." is that it is emotive and runs the risk of being read, rightly or wrongly, with a condescending and patronising tone. Read one way, it sounds quite offensive; read literally and without emotion, it's not. Perhaps it would have been better written as "I think you're mistaken, because...", to avoid the risk of upsetting people?
The other problem is that the posting is as dogmatic as the one being challenged. And I'm not sure the issue is so clear cut.
To my knowledge, the "rules" on breaking advance journeys have not yet been tested in a County Court, so whether they are valid and enforceable is purely speculative. A court may well consider that, effectively telling someone you can't get off early without paying more money, is an undue infringment of their rights. Or they may not. Who knows until this is actually tested in court or looked at by the Office of Fair Trading.
I guess we have to wait for the day that someone gets off early because they take ill and some jobsworth tries to enforce the "rules", and there is an almighty fuss in the press about it.