Sexism is something that is rampant in the whole tech industry. I feel bad about it, but I don't see how YC or HN is responsible for policing the posts.
Sure, you could have a report button and couple of mods to look at them and approve or reject. That model however is not scalable and downright silly.
The bigger issue is with the society and people's mindset and it is up to the people to not be sexist.
Having said that, I don't think any business has to do anything special for being inclusive to sex/race/gender etc. Businesses run on profits, talent generates profits. Sure, capable people should not be denied opportunity, but incapable people should not get preferential treatment and held against a lower standard.