In OStatus 'salmons' are messages sent from one server to another that contain posts. They are signed, so the receiving server knows if it can trust it.
If person peter@example.com mentions bob@differentsite.org, a salmon is sent from example.com to differentsite.org containing the message. The endpoint that this is posted to is the 'salmon endpoint'.
Using a second endpoint for privacy enhanced messages would have the way to go. Old servers wouldn't ever receive private messages, while new servers that understood the extensions could have kept 90% of their old code and infrastructure.
Oh that's nice, thanks for the explanation. I'm currently working on a social network and I like the idea of being able to connect with other ones via open standards. I need to do more research on implementation.
there's #social on freenode, although it's not very active. You might have more luck asking your questions on #pleroma on freenode (another Ostatus/AP server) or on the mastodon discord.
