TL;DR: Aphyr talks at length about how riak is not a CP system, even though nobody claims that it is. Riak is AP. Aphyr demonstrates how this plays out in practice and gives an intro into CRDTs, which let you achieve something that is eventually correct for certain kinds of state transformations.

Every conclusion he comes to are also described on Basho's site when it comes to using last-write-wins. At the end of the post, notice CRDT's preserve 100% of writes, and the same could be had if allowing siblings. Punting on high-availability is different than the company being upfront about the tradeoffs.

What do you mean? Are you saying it because Riak with sibling preservation is actually one of the few (if not the only) database that didn't drop writes.

So, what do you do with siblings in a searchable text index (the case that ElasticSearch is designed for)?