The community well reflects the technical modularity. But I feel like this is an accurate statement in the sense that the community has a strong core group of developers who make many of the decisions and a set of contributers on the fringes who. The technical modularity works very similiarly in that there is a group of core developers that do the majority of the work and others on the side contribute bug reports and comments on parts that aren't working.
The structure of collaboration in Hypothes.is is asyncronous, with a lot of the updates and pull requests happening in a stagger. However this is from a design point of view, where the work was done and reviewed in a waterfall manner. The icons were made, reviewed and implemented, and then pulled afterwards. I'm not as familiar with how it would normally be under most circumstances with coders.