Bear in mind that this was almost a decade ago, and I wasn't directly involved. With that caveat: the core mechanisms for client / server coordination in Kix were a direct descendant from Trix (short for "Matrix"), which was the original code name for Google Sheets. And Kix was developed by a team in New York, an offshoot of the Trix team which was also in New York. Writely (post-acquisition) was in Mountain View, and Wave was in Australia (I forget which city), and the picture that might give you of how closely the various teams communicated is probably accurate.

I don't know whether Trix originally used OT specifically, or the Kix team borrowed that idea from Wave. But the basic idea of clients performing small, tidy logical operations and then synchronizing them in realtime through a server was part of both Trix and Kix. Writely used a very different (and more primitive) approach.

I don't know anything about the origin of the comments feature, but my guess is that there was no connection to Wave, except (again) possibly a bit of inspiration. The Wave team was very separate, both geographically and organizationally, and the tech stack they built was very disconnected from anything that was going on with Trix, Kix, or Writely.