Oh MOS, you're a wonderful addition to my life. Sincerely.
I think that while Maron is neurotic and self-centered, I also think he exaggerates that for effect on the show, and I feel like the people who know him and go way back buy into that for comedic effect.
Tom once said during one of the external radio and/or podcast interviews that people have pointed to that he finds it odd how people think they know him because they hear him three hours a week on the best show, and I think the same idea applies. There are certainly aspects of Tom that come through on the show, but mostly, as he has pointed out in these external interviews, we don't know him, at all. My sense is that he's playing a sort of super-exaggerated version of a very limited number of aspects of his personality, but I am even guessing at that.