So, to save everyone the time, the 'no asshole' rule means they don't accept assholes and has the obvious benefit that there aren't many assholes in the 'alumni'. That's it.
How do they know who is an asshole and who is not?
It's usually rather obvious just by chatting with someone for more than 5 minutes. It's also more obvious to those who aren't themselves assholes... YMMV
We ask Jessica, who has near perfect judgment of character.
Is she available for contract work?
Actually she does often do this for YC-funded startups that are hiring people.
I can see how you could tell that most of the people she told you to hire ended up as non-assholes, but how do you know that the people she tells you not to hire would actually have been assholes?
That's an opportunity cost, and it turns out that the main thing to understand about opportunity costs is that nobody thinks about them the right way (including me, of course).
Does she have some specific criteria, or is it like the infamous Supreme Court definition of pornography? ;-)
for me, it was impressive that he was modest - in noting (a couple of times) that there are exceptions.