I think what is missing is the practical application people need to have of ‘common sense’. Hardy uses an example that is brief and to the point. It is up to the reader to provide the backstory. ONLY reading this post and following it to the letter would be foolish. It is meant to be information used appropriately by each reader.
Just as Hardy advises to not follow the advice of everyone, neither should we take any information as absolute as written.
Hope this makes sense.