Thanks for your answer ??
All you have written indicates that there is a communication in the direction from JetPack plugin to WordPress.com: There is a new post, the JetPack plugin sends anything to wordpress.com and gets an answer. To do that you need a (public) interface on the wordpress.com side. But my question is: why must I open an interface on the side of the jetpack plugin?!? That sounds like if the wordpress.com server contacts the wordpress/jetpack installation. That’s for me the wrong direction …
On the other hand I don’t know if it’s needed to send post data to wordpress.com for calculating statistical data, do image optimizations and subscription management and so on. All these things can be also done by the wordpress (JetPack plugin) installation by self.
One of the few things for sending data to wordpress.com is for me spam and virus protection of posts and attachments.
The functionality of the JetPack plugin is very good and very comprehensive. It’s probably one of the best plugins for WP. But I really don’t know if the use of this plugin can be recommended.
Thanks and regards,
Steffen