What joins them together is that they all have heart. They are written directly and with sincerity, and with no purpose other than to communicate the author's view to the world.

To me this seems the opposite of the vast majority of messages encountered in daily life, ninety nine percent of which are designed to manipulate the audience in some way. Instead of giving a sense of the author most such writing seems designed according to its target, and with the goal to shape the reader into some form or cause them to take a certain action. Advertisements are the most obvious example, lacking any sincerity whatsoever. But the description extends to political statements, magazine articles, email, newspaper reporting, graffitti, and just about every other written text. They all tend toward the artificial.