User blog comment:DaNASCAT/Technical Update: March 20, 2012/@comment-3441771-20120326063434/@comment-3508190-20120327065946

That's psychology. As long as there's no button, you can't reply to sub-comments because... well... there's no button. But once you add the button, people will start asking why they cannot reply.

"Why not? Because you can't. It's a design decision." &lt;

&gt; "Yeah, but you already have a reply button!"

"That's not a reply button. That's a view source button" &lt;

&gt; "Huh? Who needs that?"

"You might. It's interesting." &lt;

&gt; "You don't understand! He called me a poo brain! I need to reply!"

(I'll leave the rest of the dialog up to your imagination...)