@pfefferle @daniel For star/like, there are existing WP plugins that add like buttons. The way I imagined this working was cooperating with an existing plugin. So the AP plugin calls a hook to say "just got a like for this thing". If you don't have a "like" plugin nothing happens, but if something's listening the like shows up on the page.
I say this because I'm involved with a WP events site and really interested in AP's "event" feature. But you wouldn't want the AP plugin to implement the details itself. If you take the approach of delegating wherever possible, the WP ecosystem could enable all kinds of cool stuff while keeping the AP plugin itself lean.