> But Usenet had threads, .... Yes, using the "References:" and/or "In-Reply-To:" headers. Later clients tended to do this, I think. > ... to get the benefits

> But Usenet had threads, .... Yes, using the "References:" and/or "In-Reply-To:" headers. Later clients tended to do this, I think. > ... to get the benefits. Yes, and the drawbacks: in-depth discussions involving multiple people were harder to come by. In any case, in both Usenet -- late in the game -- and many mailing lists, there are relatively few participants, so scaling is not really an issue.