Now it's not so convincing piece of advice when you say "Never do an accelerator", when you just applied for one and got rejected, is it?
YC has always valued persistence - so I'm sad that he applied and wrote that, since he might have been able to get in the next time, and I think YC likely would have helped his ability to recruit and valuation, especially given the changing markets. But regardless, I always have respect for startup founders (esp after 3 years of hard work) - so we should all wish his team luck.
I totally agree on the cognitive dissonance with bashing YC and saying to never to do it, after getting rejected recently. But I can realize how it might not be a fully rational perspective (he'd probably argue that he's more educated now, and that's why he's changed his mind since applying - my gut is there's some emotions involved, since I can't see a ton of benefit to him to write this so publicly).