Yea, this last one was the second one, but the first one was 10 or so years ago.
Quoting a post notifies the person quoted that they have been quoted (answered or otherwise referred to) that persons post .
Using @TrailBeast anywhere in the post for example, notifies me that that I have been mentioned in a post.
If people just type something after another post the person doesn't get any notification that there is anything new, it's a crapshoot whether they ever see it or not.