IANAL, but that arbitration clause doesn't sound remotely enforceable to me. Regardless, that they put it in there is more than good enough reason to not use the site.
> You agree that any and all disputes or claims that have arisen or may arise between you and Y Combinator, whether arising out of or relating to this Terms of Use (including any alleged breach thereof), the Site, any advertising, any aspect of the relationship or transactions between us, shall be resolved exclusively through final and binding arbitration, rather than a court, in accordance with the terms of this Arbitration Agreement, except that you may assert individual claims in small claims court, if your claims qualify.
> YOU AND Y COMBINATOR AGREE THAT EACH OF US MAY BRING CLAIMS AGAINST THE OTHER ONLY ON AN INDIVIDUAL BASIS AND NOT AS A PLAINTIFF OR CLASS MEMBER IN ANY PURPORTED CLASS OR REPRESENTATIVE ACTION OR PROCEEDING. UNLESS BOTH YOU AND Y COMBINATOR AGREE OTHERWISE, THE ARBITRATOR MAY NOT CONSOLIDATE OR JOIN MORE THAN ONE PERSON’S OR PARTY’S CLAIMS AND MAY NOT OTHERWISE PRESIDE OVER ANY FORM OF A CONSOLIDATED, REPRESENTATIVE, OR CLASS PROCEEDING. ALSO, THE ARBITRATOR MAY AWARD RELIEF (INCLUDING MONETARY, INJUNCTIVE, AND DECLARATORY RELIEF) ONLY IN FAVOR OF THE INDIVIDUAL PARTY SEEKING RELIEF AND ONLY TO THE EXTENT NECESSARY TO PROVIDE RELIEF NECESSITATED BY THAT PARTY’S INDIVIDUAL CLAIM(S).
HN doesn't even offer the ability to opt out of arbitration, so it's even worse than Quora in this aspect.
You're right, though, the arbitration clause is awful.
I don't really have any interest in going down that particular road, but that's one of the hiccups these sorts of contracts hit when faced with real world legalities.