On one panel, reply-indent guide lines draw per depth, a like-click rolls the digits and pops the button elastically, and a delete folds the row as the rows below spring up — demo

SunsetSkipper

Three motions share one panel here.
RainbowBridge

The reply indentation shifts in proportion to depth.
DewShaker

The nested-reply guide lines draw top to bottom.
RockCrevices

Delete this comment and the rows below spring up.