In theory I like the idea of decentralization but in practice I haven't seen it work out well. For example email didn't become prolific until large centralized players became the dominant force. I see federation/decentralization being better as a late feature in software. Through centralization you can move a lot faster, which in the case of Signal is extremely useful. They wouldn't be able to provide the product they have with decentralization. That's why Moxie has been against decentralization. Maybe I'm wrong, but I don't see chat apps as having an unbounded number of features. As I see it once Signal moves into more of maintenance mode then we can talk about federation, by allowing outside servers being able to communicate to the main Signal server. But for now it seems better to focus on getting people to the platform and if we're talking about it from a privacy and security point of view, this is the higher priority. Decentralization doesn't provide much more security while Signal is still trustworthy. There's bigger fish to fry right now.