Pingbacks and comments can work like little packs of karma. Using Ping-O-Matic natively, WordPress notifies you that your content has been linked to from another user on a different site. This typically happens in the form of a comment or post reply. You write an awesome post and a site visitor reads that post, prompting him or her to write a response and linking back to you. Plugins such as subscribe to comments can certainly add more engagement to let subscribers connect with you by getting notified every time there is a new comment on your awesome post, thereby, tempting them to write a new comment on your site. But it shouldn't stop there. You have to be proactive about your pingbacks and comments. Take the time to thank each commenter individually to let them know you care about his or her opinions regardless of whether they're good or bad. This is the equivalent of thanking guests for attending your party after they leave. It lets them feel more appreciated so they'll return. In contrast, deleting comments should also be discouraged, as it appears that your site is censoring or hiding content.