Element/Matrix/Gitter is a great IRC-replacement and public chat, Mastodon is great as a decentralized Twitter alternative, IPFS is great for decentralized public file sharing. Default-public services like this probably have an easier time being decentralized. It'd actually be nice to see thoughtful integrations between these three IMO.
The greatest advantage Signal has is probably doing same-day updates for all clients while being dead simple to use well. A decentralized protocol could achieve these things, but none have yet. Still I hope someday soon we can have everything be decentralized, but like the blog post says, we can't let the perfect be the enemy of the good.
Federated, not decentralized. Decentralized is peer2peer like torrents. Federated is like email where there are little fiefdoms like Gmail, yahoo, or self-hosted.
that definition seems like a bit of a stretch: decentralized does not mean anything more than not being centralized.
Federation implies decentralization.
Be kinder, these semantics differences are newer(ish) developments and not everyone knows the area. It's a bit confusing to say federation does imply decentralization point blank.
For a long time, federated architecture was seen as special case of decentralized, for example in designing stuff for internal use. It still makes sense in that context.
In the context of larger external facing systems, I've found it useful to think of federated as "partly decentralized", and "decentralized" is short-hand for "fully decentralized".
The greatest advantage Signal has is probably doing same-day updates for all clients while being dead simple to use well. A decentralized protocol could achieve these things, but none have yet. Still I hope someday soon we can have everything be decentralized, but like the blog post says, we can't let the perfect be the enemy of the good.