<h2>this is a tweet
<h3>this is a reply to h2
<h4> this is a follow up to h3
<h5> this is another follow up to h3
/th h3
<zz0>this is a tweet
<zz1>this is a reply to h2

what u can see with new twitter and other apps is :-

/replies (hypothetical)
<zz0>this is a reply to h2
<zz1>this is a follow up to h3
<zz2> this is another follow up to h3