If "there's also a feed of everyone's posts together," I see that a small group of writers could collaborate on a topic of concern in a single instance of rss.chat, creating something they think of as a single-topic publication.
This could be a topic of pressing short-term interest, and that response would be nimble, wouldn't it? When a weather disaster threatens a region of the country, for example, the tools are already in place here and there's a low barrier to entry for new writers to contribute. The feed would send the posts to a WordPress blog built in minutes for the occasion, yes?
You got it. Groups of writers. As small as one.
But, in a while it won't matter if they're on the same instance.
You could form a virtual group, using people on different servers, maybe not even running my software.
When my students and I studied historical episodes of active citizenship, we saw that six things needed to be in place for the activists to have a chance for success.
One of them was the ability to affiliate with others. Not just write as we please and read what others write. Beyond that: to find partners and allies and take on the shared work of effective citizenship, through public speech and private planning, just as historical examples have shown.
By now we take for granted that we can read and write as soloists on the web. Looks like rss.chat, however, is taking a very practical step forward in the power to affiliate.