@evan i think you know where i already stand on this, but instead of recursively crawling replies collections it would be better if alice had a collection that alice owned and contained a flat set of whatever alice wanted to be in it.
i think "bob gets to choose" is not inherently problematic insofar as alice never actually established any context. bob's post stands on its own, with any arbitrary audience. if there *was* such a thing as "alice's convo" then it can/should have its own audience.