Hello,
I understand that your plugin doesn’t store comments to the DB but surely it connects with the DB in some fashion (even simply to acknowledge that it is activated, or to view the FB account details).
I’ve deactivated all other plugins that are remotely related to Facebook, and when I enable your plugin my DB connections immediately start to increase and they do not seem to get closed. Seven new connections in under 30 seconds. This would be fine if they were closed, but they do not. All we can do is either kill the connections or wait for them to eventually time out.