We have some people who got in last time chatting with us and doing mock interviews here: <a href="https://communities.metachat.com/communities/ycombinator" rel="nofollow">https://communities.metachat.com/communities/ycombinator</a>
Not yet. Come join the chat room for YC S18 applicants : <a href="https://www.hackerschat.net/" rel="nofollow">https://www.hackerschat.net/</a>