Following is the JSON which i have received from realtime update
{"id":"this is the page id","time":1390189044,"changes":[{"field":"feed","value":{"item":"comment","verb":"add","comment_id":"10152572606743677_340941814","parent_id":10152572606743676,"sender_id":113833593676,"created_time":1390189044}}]}]}
the weird part is the parent_id is 10152572606743676 and comment_id starts with 10152572606743677 which are totally different and this doesn't happen for all the pages and happens only to a specific pages from facebook
It might be connected with pages having global and localized versions. For this reason the parent id is the global page id and the first part of the comment is the localized version id where the comment is made. Since I can't fetch those IDs it's like shot in the dark but it's worth to check it.