How to listen for comment events

The solution is to implement an OSGi event handler.  Here's a sample event handler implementation.

In your event handler you would listen for this event topic:
com/adobe/cq/social/comment

You could optionally filter for these event types using the Event Filters OSGi property (this is an optional property as you could use logic in your handleEvent method to do the same):

POST member creates a comment
ADD member replies to comment
UPDATE member's comment is edited
DELETE member's comment is deleted