Disqus commenting activity can be captured via callbacks, by using:
function disqus_config() {
this.callbacks.onNewComment = [function() { trackComment(); }];
}
Where you will replace trackComment(); by your own function.
Here is an example that loads Disqus comments dynamically using JavaScript, where you can find the discus_config function that will be fired when a new comment is added.
var loadDisqus = function() {
window.disqus_identifier = 'your thread id';
window.disqus_shortname = 'disqus_shortname';
window.disqus_url = 'http://your_domain.com/path';
window.disqus_title ='page title';
window.disqus_config = function() {
this.callbacks.onNewComment = [function() { myFunction() }];
};
(function() {
var dsq = document.createElement('script');
dsq.type = 'text/javascript';
dsq.async = true;
dsq.src = '//' + disqus_shortname + '.disqus.com/embed.js';
(document.getElementsByTagName('head')[0] ||
document.getElementsByTagName('body')[0]).appendChild(dsq);
})();
};