I've said this before, but while I know for a lot of people Reader is the axed Google product they miss most, for me it will always be Wave. I know a lot of people didn't get it, and I can't blame them, but I was part of a six-person software team using Wave for a brief project and, despite its faults, it was the greatest communication tool any of us had ever used, and remains so to this day. Slack/Discord/Teams/Trel…
What made Google wave so great to you? (Even better than slack/Discord/Trello)?
I also like that comments were a first-class citizen; part of the document. You could have an in-line conversation about a paragraph, then distill the results into the text and delete the conversation. Comments weren't another "mode" like they are in Google Docs; they were just document bubbles nested in a parent document bubble.
I've apparently flip-flopped on this; looking at a post I wrote at the time, I thought it felt wrong to delete comments.