I think that would require a tweak to the UI to make it more obvious that a tweet is a reply. There's already some subtle stuff there (small-font "in reply to"

I think that would require a tweak to the UI to make it more obvious that a tweet is a reply. There's already some subtle stuff there (small-font "in reply to" and I think a little curved arrow), but the most obvious part that the content starts with "@".