Most other posts on HN don't involve such degree of mudslinging. When they do, I think you'll find similar questions being asked.

I don't really think is is mudslinging. He purposely left out the company's name, and YC as a whole won't be hurt by this - there have been enough YC successes that I'm sure everyone here would consider a YC startup to be better than the average startup.

This is just one engineer warning people that you should still take a solid look at a company before you hop on board, even if it is a YC startup.