It looks like there some good material here about relays. It mostly overlaps with what I have. One aspect that’s not covered (unless I missed it), is the JSON LD Signatures required for many of the messages passing through the relay. [Mastodon documentation]
We might also need to agree on some core terminology. It looks like pub-relay defines message forwarding and message relaying and I don’t fully understand the significance of the distinction at this point. Other relay implementations simply “relay” messages. I also would like to avoid writing this in terms of Mastodon (or Pleroma) specifically, but I don’t have a good generic name for a server that publishes to and consumes from a relay server.
Any ideas about how to proceed? Do we merge the material? The blog article (which looks good) is typically a different type of document than an FEP (less conversational). It could be useful to have an informational FEP and one or more related blog articles.