Julian from Design Create Play wrote a wiki article on how to write plugins for NodeBB. The plugins system as a whole is a pretty barebones module which we will work on improving as time goes on. That said, there are already quite a few plugins available which are installable via npm.

A third party plugin for parsing BBCode by adarqui is already under development, which is pretty exciting. Hopefully we can see more NodeBB plugins from developers as time progresses.