It can be tough to wrap your head around Reactive Extensions, and by extension ReactiveUI, when you start out. As with any new technology, there are some pitfalls you fall into as you learn.
Over time, GitHub has learned some hard lessons by failing over and over again as they built GitHub for Windows. All those failures are interspersed with an occasional nugget of success where they learned a better approach.
However, much of this knowledge was tribal in nature. Stories were linked to each other as reminders of what to do and what not to do. But that's fragile and doesn't help anyone else.
GitHub has since released their design guidelines for building an application with ReactiveUI so there is a record of that tribal knowledge. This way others can benefit from what they learned, and they can benefit from what others learn.