Ebarnacle, that's the whole point. It's a test. And if you fall for the "It hasn't done me any harm, therefore it's not so bad" bit, then you've failed the test.
I disagree with you about sin and intent. If you could reasonably have seen it coming, then yes - that's a sin of omission. But if you've made a real effort to avoid it happening and it *still* happened despite all your preparations, then it's down to you to assess whether you could have done more to prevent it happening. If you think you could, then it's a sin for which you may feel some atonement is necessary. But if you think, honestly, that there wasn't any more you could have reasonably done, then I don't believe it can be considered a sin (and note the "honestly", because trying to fool yourself is itself a sin). That seems to be confirmed by Rabbi Sol saying, "Those individuals who have unwillingly and unknowingly eaten "Treif" as a result of being misled in this instance have not committed a sin."
I also disagree with that orthodox line on "it has to be hard for it to be good for you". As you said earlier, some of the Jewish rules are pure common-sense for an age without refrigeration, sterile conditions, good cooking equipment or any good way to clean things properly. I think there's an urgent need to differentiate between those kind of rules and the *moral* rules of "thou shalt not kill" and the like. That comes back to what I said on the other thread - if a religion fits exactly what you believe, then that's fine. But if a religion says "now you're one of us, you must do a lot of illogical things otherwise you can't stay as part of the gang", then it becomes a means of control rather than a means of praising God. On that, I agree with LH - refrigeration and all those other good things have made many of those non-moral rules irrelevant. For any religion to stay relevant, it needs to not only add new standards for moral conduct when new situations arise (eg. IVF treatment) but also be prepared to ditch old rules when it's clear they no longer apply. That's why there's such an urgent need to establish which rules are "core" moral rules that are inviolable, and which rules are "current situation" guidance for how to behave morally in the world as it currently exists. Leviticus is the classic example of rules created by Man for health and safety purposes, which are interesting from a historical perspective but utterly irrelevant to modern life.