Sign language is also useful. Let’s start with the basic use case: talking without making noise. This is obviously useful if you’re in a situation that demands silence, but perhaps less obviously, it helps in noisy environments, too!

Some hand gestures to communicate basic messages and location specific behavior is great. like we have going to bathroom, agreeing with you, or talk to the hand. but I do not understand why we need a full language including gestures for individual letters. 

I learned ASL alphabets and common words but have largely forgotten because they are never used in daily life. but I want more hand gestures. one that comes to mind, change the topic of conversation since the current one is boring.

The text provides examples of how very small messages contain whole lot of subtext.
This is true but  these are very hard to decipher for me. And I have a suspicion that others with high social intelligence are not very good either. 

I generally abstain from finding the Straussian meaning of everything a person says. 
There is a lot underneath a person's message with many unknown unknowns.
Instead, it is much better to have strict guidelines for yourself when communicating (although they are enforceable over text. It all goes by the wayside during conversation). It might be costly to me in many situations but they provide sanity by removing ambivalence.

Alexey's blog on follow up (https://guzey.com/follow-up/) states, it is acceptable to remind someone 2 times and occasionally 3 of your message.
I have adopted this to ask girls out. If she mentions she is busy, you could ask her out again. but not the 3rd time, except in rare situations. 
This has also protected from the guilt of nagging someone.

We should be able to create such rules for many types of social interactions that are not context dependent. 

Whenever there is a negative personality trait mentioned (various ways people hurt others psychologically unintentionally), I start thinking if I am one of the perpetrators. Psychological Hypochondria if you will. 
It is very difficult to diagnose oneself of vague sensibilities and behaviors. And hence, much more difficult to correct.

the post is very informative and thought-provoking. and although the headline states that the article contains more than you wanted to know about the Swiss political system, I am curious and want to know about it more. which books would you recommend for reading further on the topic? which books did you read to research for the topic?

thanks