bower install nebula
This is a library for creating force-directed graph interfaces for viewing and interacting with nested comments.
It allows you to build stuff like this 
Really, it's just a wrapper around the d3 force-directed graph layout, but it makes some opinionated choices about the best way to interact with comments as force-directed nodes and so the idea is that there's a lot of usable functionality pre-made at the expense of some customizability.
There's a project ready-made for testing it here
// Our data
var nodes = [
{
_id:0,
target_id:undefined,
value:1,
author:"me",
body:"first!"
},
{
_id:1,
target_id:0,
value:2,
author:"you",
body:"second",
extradata:"asdfasdf"
}
]
// Preparation
var width = 800;
var height = 600;
var body = d3.select("body");
body
.append("svg")
.attr("id", "graph")
.attr("width", width)
.attr("height", height);
var onmouseover = function(d){
console.log(d);
//node's information is logged
}
//actually initialize the graph
nebula = new Nebula("#graph", width, height, onmouseover, nodes);
var newNode = {
_id:3,
target_id:0,
value:1,
author:"you",
body:"third"
},
//adds a new node to the graph.
nebula.addNode(newNode);
//removes the node with id 1
nebula.removeNode(1);