This Forum Comments System add-on allows users to post comments under a reply in the forum. The add-on basically functions as nested replies for the main reply in the tread, suitable also for Q&A threads.
This FCS add-on combines similar functionalities as you can find in vB5, Facebook and xF2 profile comments.
There are already 13 user group permission options available now organized in a dedicated section. Notification, alerts are sent no matter where the comment is written, whether it is in a new or an old reply.