I also think that there are similarities here to the 'sister' Reddit community/mentality (especially r/programming which is cross-posted back and forth regularly), in that people are willing to support people that they personally identify with or like. I don't see that as detrimental to a community, but rather as a key element in fostering community (unless it gets too insular and discriminating in who is able to get that treatment). Any news about a Ycomb grad will rise to the top because of the tight-knit culture and identifying with each other from the early stages of their respective companies, so I don't see any issue with someone posting to the community with a transparent "this is my post" statement by someone from outside the group of grads.

Regardless of previous success, I think we can appreciate someone who is still excited by a new opportunity and sharing his content for anyone who might find value and/or support his quality content. Many financial fundamentals have been taught before, but can be repackaged and interesting and valuable to readers, especially those who haven't read his book (which I haven't). Like Mike says here, some overly promotional agendas get drowned out, but there is also a certain amount of community appreciation for people who just come out and say "this is something I made, what do you think?" Of course, in a social voting system, if people think "wow that sucks" then they downvote the content and leave a "that sucks" comment.