At times it is an uncomfortable watch (more so if you listen to the full audio of the performances this film references), Harmon is a canny student of human nature and knows how to be cruelly funny, the tragedy is he can also see how this damages and hurts people around him.
But the film brilliantly only uses him as a focus. It asks many people to describe him and they are lost for words, but interestingly when asked to say what they think he would describe himself as, suddenly they find the words and a picture emerges. This serves as an analogue for why he and his works have become passionately loved (by few perhaps, a joke about Community's ratings gets a big laugh, but a dedicated few). He serves as a prism of understanding. People connect to him and his work through it's seeming honesty. They find stories that tell them who they are, not just the who characters are on screen.
This sense is relayed through the film in many ways but most particularly in the story of Spencer Crittenden, a young uncomfortable but funny and oddly charismatic man who has a fame of sorts thrust upon him. Harmon at one points frames Spencer as the hero, himself as the villain but this is just a device (as Harmon well knows) to say both are human.
People want nothing more than to be feel a connection, to feel they have an impact on the world, that they matter.
And Harmontown tells us we do.