Google Wave may not have picked up, but Google Docs certainly did. In the broader topic of online discussion, I feel like we'd be remiss if shared Google Docs didn't get a mention. (I assume MS O365 has a similar set of features, but I haven't used it extensively, so I'm avoiding using a generic term here, at the risk of sounding like a commercial.)
Usually, a heavy email thread will start with a multi-paragraph essay, and try to get to some sort of consensus from the participants. Where google docs lets users comment on a specific phrase or word, and have a discussion thread based on that highlight, Google Docs makes it possible to have a conversation about a specific part of the document. By allowing for shared editing, Docs allows someone who came later to rewrite words or phrases (if that user is allowed to).
If I'm working on any sort of a doc - engineering design doc, marketing copy, whatever - with multiple people, both email and slack fall short compared to a Google Doc. It's got a specific use case, so it's not remotely a replacement for slack or email, but there's a lot of good, focused communication happening in those comment margins.
Usually, a heavy email thread will start with a multi-paragraph essay, and try to get to some sort of consensus from the participants. Where google docs lets users comment on a specific phrase or word, and have a discussion thread based on that highlight, Google Docs makes it possible to have a conversation about a specific part of the document. By allowing for shared editing, Docs allows someone who came later to rewrite words or phrases (if that user is allowed to).
If I'm working on any sort of a doc - engineering design doc, marketing copy, whatever - with multiple people, both email and slack fall short compared to a Google Doc. It's got a specific use case, so it's not remotely a replacement for slack or email, but there's a lot of good, focused communication happening in those comment margins.