We haven't had much contact with the STC. Their meetups generally cost money, and are focused on DITA and more "old school" XML based technology. We are trying to bring the world of devs who care about docs to the doc writers, and make beautiful things in the process. Styled as an open source community.

We haven't had much contact with specific style guides. We have lots of people from companies that attend. It sounds like a great topic for one of our meetups or conference :)