The Fat Doctor Problem

A person who failed usually knows much more about how not to fail than a person who succeeded.

So I largely disagree with the opinion of the author.

I agree with sssilver in his disagreement, but there's a nuanced logical flaw here that's not even being addressed.

sssilver brings up that someone who has experienced failure in x isn't necessarily a poor source of advice in x. Similarly, just because someone was successful in x doesn't mean that they have any clue what they did right.

A more defensible bit of advice would be to evaluate someone's credibility before taking their advice, but I can't think of a more obvious truism.