How? I guess you could use it like a chat room just putting new messages at the bottom of the document but seems like a crazy kludge to use Wave as a chat.

I thought that was its intended primary purpose. We could chat and inline media, pictures, etc. It was a big upgrade from IRC. There were issues with sharing files larger than just images and whatnot, but it easily could have been polished a bit into something better. If Discord added the ability to have 'threads', it would basically be what we used Wave for. For a few weeks anyway until Google decided it wasn't catching on enough or whatever justification they gave for giving up on it.

I don't think I ever heard of it being pitched that way just as a collaborative editing room for editing an actual document not just for using the comments etc as a chat.