In reply to PatParslow.

"... is the way that as a conversation proceeds a whole thread is promoted back to the top of the stream as a new comment or interaction comes in."

This Quora thing kinda does that, but has the bad aspect that it keeps the earlier notification, and that it only shows the last addition, thus eliminating the context... but thanks for bringing it up! It's indeed one good feature to like or not like services!

One thing any service should have too, is a best-of-the-day summary... but I think that falls under your not-everyone-can-follow-the-live-flow paragraph...