Thank you. I understand now, but I have to say that I think your documentation is unclear about this. I now understand what you mean by this line from your post announcing dev mode:
With this, features that do not require a connection to WordPress.com servers can be activated on a localhost WordPress installation for testing.
It would have helped me and might help others like me if you listed on your site or indicated within the Jetpack admin screen which modules can work offline and which can't. I gather you must have decided that "there's no Activate button" is enough to convey this point. I'd suggest adding something to tell devs WHY there's no Activate button.
Thanks for responding. I hope my feedback proves useful to you. And thanks for the awesome plugin.