The good news is that it seems they have some leverage on Amazon now.

"Hi Mr. CIO of Amazon. You realize we had a 6 hour outage on one of the largest sites in the US because of you. We don't want to badmouth your service but we can. Care to pay more attention now?"

Reddit's no longer a cashstrapped startup with limited resources and options. It's ultimately their choice to stick with Amazon. If Amazon has been giving them the run around for more than a whole year, maybe it would've been a smart decision to move to something else.