@Daniel No, Mastodon admins don’t have any more (or any less) powers than Friendica and Diaspora. An admin of any of these platforms can read DMs sent and received from/by their server given a modicum of technical know-how.

From my experience Mastodon sounds as cumbersome to install as Diaspora, Friendica being on the easier side.

Speed-wise, Mastodon is definitely snappier than both, not sure if it’s because it’s more efficient or generally installed on more powerful servers though.