Reading these and thinking about how they are still very applicable to general conversation today, I can't help but notice that they state the rules in such a way that the ego of the person reading them remains intact. One strikes me in particular:

9. A man of real intelligence and cultivated mind is generally modest. He may feel when in everyday society, that in intellectual acquirements he is above those around him; but he will not seek to make his companions feel their inferiority, nor try to display this advantage over them. He will discuss with frank simplicity the topics started by others, and endeavor to avoid starting such as they will not feel inclined to discuss. All that he says will be marked by politeness and deference to the feelings and opinions of others.

While it is certainly in poor taste to flaunt your intelligence, it is also a very common for someone to think they are of a superior intellect when they are really not, in which case trying to seem intelligent the person would just embarrass themselves. I think it strikes me because in may cases these are phrased so that most of them are asexual or gender-neutral, but trying to keep the reader's ego intact seems like a very masculine way to present the rules. It would be interesting to see how these exact rules (not a feminine conversation guide of the time) would be phrased if they were directed to a female reader.