This post seems like making a mountain over a molehill to me. The poster may have a point about the candidates, I don't know, but the deploy was hardly "disastrous." A site, still in beta mind you, releases an upgrade that has some problems. They're quick to take user feedback into account and change things accordingly. I still don't see anything the AO3 did that they need to collectively apologize over, and it's unfortunate that they felt they had to.

But thanks for linking to this so we could get some insight into this apology.