> The most hopeful case is that there is ONE place that isn't 'strictly append only', and that's, for lack of a better term, the 'main pointer'. Which hash is the actual state of the app as it should be compiled and deployed right now?

I think that's how it works. The way I understand it from reading the tour, there is a separate store for the code and for the name mappings. Both main functions would merge without conflict into the code store, but the mappings would conflict.